diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index 7a6aaa1861859..b55edb31276eb 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -248,6 +248,16 @@ namespace ts {
 
             if (!file.locals) {
                 bind(file);
+                // `bindSourceFileAsExternalModule` is called in `setCommonJsModuleIndicator`,
+                // but if `setCommonJsModuleIndicator` was not called, as it won't be for `.cjs`
+                // files with no imports or exports, then `bindSourceFileAsExternalModule`
+                // will not have been called, which would cause the checker to crash.
+
+                // This also can't be moved to `bindSourceFileIfExternalModule`,
+                // as that gets called after CommonJS exports are bound.
+                if (isCommonJsModule(file) && !file.commonJsModuleIndicator) {
+                    bindSourceFileAsExternalModule();
+                }
                 file.symbolCount = symbolCount;
                 file.classifiableNames = classifiableNames;
                 delayedBindJSDocTypedefTag();
@@ -283,7 +293,7 @@ namespace ts {
                 return true;
             }
             else {
-                return !!file.externalModuleIndicator;
+                return isExternalModule(file);
             }
         }
 
@@ -2154,7 +2164,7 @@ namespace ts {
                 return Diagnostics.Identifier_expected_0_is_a_reserved_word_in_strict_mode_Class_definitions_are_automatically_in_strict_mode;
             }
 
-            if (file.externalModuleIndicator) {
+            if (isExternalModule(file)) {
                 return Diagnostics.Identifier_expected_0_is_a_reserved_word_in_strict_mode_Modules_are_automatically_in_strict_mode;
             }
 
@@ -2223,7 +2233,7 @@ namespace ts {
                 return Diagnostics.Invalid_use_of_0_Class_definitions_are_automatically_in_strict_mode;
             }
 
-            if (file.externalModuleIndicator) {
+            if (isExternalModule(file)) {
                 return Diagnostics.Invalid_use_of_0_Modules_are_automatically_in_strict_mode;
             }
 
@@ -2244,7 +2254,7 @@ namespace ts {
                 return Diagnostics.Function_declarations_are_not_allowed_inside_blocks_in_strict_mode_when_targeting_ES3_or_ES5_Class_definitions_are_automatically_in_strict_mode;
             }
 
-            if (file.externalModuleIndicator) {
+            if (isExternalModule(file)) {
                 return Diagnostics.Function_declarations_are_not_allowed_inside_blocks_in_strict_mode_when_targeting_ES3_or_ES5_Modules_are_automatically_in_strict_mode;
             }
 
@@ -2460,7 +2470,7 @@ namespace ts {
                         bindSpecialPropertyDeclaration(expr);
                     }
                     if (isInJSFile(expr) &&
-                        file.commonJsModuleIndicator &&
+                        isCommonJsModule(file) &&
                         isModuleExportsAccessExpression(expr) &&
                         !lookupSymbolForNameWorker(blockScopeContainer, "module" as __String)) {
                         declareSymbol(file.locals!, /*parent*/ undefined, expr.expression,
@@ -2743,7 +2753,7 @@ namespace ts {
         }
 
         function setCommonJsModuleIndicator(node: Node) {
-            if (file.externalModuleIndicator) {
+            if (isExternalModule(file)) {
                 return false;
             }
             if (!file.commonJsModuleIndicator) {
@@ -2866,7 +2876,7 @@ namespace ts {
                     if (hasDynamicName(node)) {
                         break;
                     }
-                    else if ((thisContainer as SourceFile).commonJsModuleIndicator) {
+                    else if (isCommonJsModule(thisContainer as SourceFile)) {
                         declareSymbol(thisContainer.symbol.exports!, thisContainer.symbol, node, SymbolFlags.Property | SymbolFlags.ExportValue, SymbolFlags.None);
                     }
                     else {
@@ -3133,7 +3143,7 @@ namespace ts {
         function bindCallExpression(node: CallExpression) {
             // We're only inspecting call expressions to detect CommonJS modules, so we can skip
             // this check if we've already seen the module indicator
-            if (!file.commonJsModuleIndicator && isRequireCall(node, /*checkArgumentIsStringLiteralLike*/ false)) {
+            if (!file.commonJsModuleIndicator && !fileExtensionIs(file.fileName, Extension.Mjs) && isRequireCall(node, /*checkArgumentIsStringLiteralLike*/ false)) {
                 setCommonJsModuleIndicator(node);
             }
         }
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 62994a8f464dd..c403f9a660a2c 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -1382,7 +1382,7 @@ namespace ts {
             const useFile = getSourceFileOfNode(usage);
             const declContainer = getEnclosingBlockScopeContainer(declaration);
             if (declarationFile !== useFile) {
-                if ((moduleKind && (declarationFile.externalModuleIndicator || useFile.externalModuleIndicator)) ||
+                if ((moduleKind && (isExternalModule(declarationFile) || isExternalModule(useFile))) ||
                     (!outFile(compilerOptions)) ||
                     isInTypeQuery(usage) ||
                     declaration.flags & NodeFlags.Ambient) {
@@ -1717,7 +1717,7 @@ namespace ts {
                         isInExternalModule = true;
                         // falls through
                     case SyntaxKind.ModuleDeclaration:
-                        const moduleExports = getSymbolOfNode(location as SourceFile | ModuleDeclaration).exports || emptySymbols;
+                        const moduleExports = getSymbolOfNode(location as SourceFile | ModuleDeclaration)?.exports || emptySymbols;
                         if (location.kind === SyntaxKind.SourceFile || (isModuleDeclaration(location) && location.flags & NodeFlags.Ambient && !isGlobalScopeAugmentation(location))) {
 
                             // It's an external module. First see if the module has an export default and if the local
@@ -1751,7 +1751,7 @@ namespace ts {
 
                         // ES6 exports are also visible locally (except for 'default'), but commonjs exports are not (except typedefs)
                         if (name !== InternalSymbolName.Default && (result = lookup(moduleExports, name, meaning & SymbolFlags.ModuleMember))) {
-                            if (isSourceFile(location) && location.commonJsModuleIndicator && !result.declarations.some(isJSDocTypeAlias)) {
+                            if (isSourceFile(location) && isCommonJsModule(location) && !result.declarations.some(isJSDocTypeAlias)) {
                                 result = undefined;
                             }
                             else {
@@ -1945,7 +1945,7 @@ namespace ts {
             if (!result) {
                 if (lastLocation) {
                     Debug.assert(lastLocation.kind === SyntaxKind.SourceFile);
-                    if ((lastLocation as SourceFile).commonJsModuleIndicator && name === "exports" && meaning & lastLocation.symbol.flags) {
+                    if (isCommonJsModule(lastLocation as SourceFile) && name === "exports" && meaning & lastLocation.symbol.flags) {
                         return lastLocation.symbol;
                     }
                 }
@@ -2467,7 +2467,7 @@ namespace ts {
                 return hasExportAssignmentSymbol(moduleSymbol);
             }
             // JS files have a synthetic default if they do not contain ES2015+ module syntax (export = is not valid in js) _and_ do not have an __esModule marker
-            return !file.externalModuleIndicator && !resolveExportByName(moduleSymbol, escapeLeadingUnderscores("__esModule"), /*sourceNode*/ undefined, dontResolveAlias);
+            return !isExternalModule(file) && !resolveExportByName(moduleSymbol, escapeLeadingUnderscores("__esModule"), /*sourceNode*/ undefined, dontResolveAlias);
         }
 
         function getTargetOfImportClause(node: ImportClause, dontResolveAlias: boolean): Symbol | undefined {
@@ -8568,7 +8568,7 @@ namespace ts {
                      declaration.parent.kind === SyntaxKind.BinaryExpression)) {
                 return getWidenedTypeForAssignmentDeclaration(symbol);
             }
-            else if (symbol.flags & SymbolFlags.ValueModule && declaration && isSourceFile(declaration) && declaration.commonJsModuleIndicator) {
+            else if (symbol.flags & SymbolFlags.ValueModule && declaration && isSourceFile(declaration) && isCommonJsModule(declaration)) {
                 const resolvedModule = resolveExternalModuleSymbol(symbol);
                 if (resolvedModule !== symbol) {
                     if (!pushTypeResolution(symbol, TypeSystemPropertyName.Type)) {
@@ -22523,11 +22523,11 @@ namespace ts {
 
             if (isSourceFile(container)) {
                 // look up in the source file's locals or exports
-                if (container.commonJsModuleIndicator) {
+                if (isCommonJsModule(container)) {
                     const fileSymbol = getSymbolOfNode(container);
                     return fileSymbol && getTypeOfSymbol(fileSymbol);
                 }
-                else if (container.externalModuleIndicator) {
+                else if (isExternalModule(container)) {
                     // TODO: Maybe issue a better error than 'object is possibly undefined'
                     return undefinedType;
                 }
@@ -22893,7 +22893,7 @@ namespace ts {
                         // Don't contextually type `this` as `exports` in `exports.Point = function(x, y) { this.x = x; this.y = y; }`
                         if (inJs && isIdentifier(expression)) {
                             const sourceFile = getSourceFileOfNode(parent);
-                            if (sourceFile.commonJsModuleIndicator && getResolvedSymbol(expression) === sourceFile.symbol) {
+                            if (isCommonJsModule(sourceFile) && getResolvedSymbol(expression) === sourceFile.symbol) {
                                 return undefined;
                             }
                         }
@@ -27788,12 +27788,18 @@ namespace ts {
         }
 
         function checkImportMetaProperty(node: MetaProperty) {
-            if (moduleKind !== ModuleKind.ESNext && moduleKind !== ModuleKind.System) {
-                error(node, Diagnostics.The_import_meta_meta_property_is_only_allowed_when_the_module_option_is_esnext_or_system);
-            }
             const file = getSourceFileOfNode(node);
+            if (fileExtensionIs(file.fileName, Extension.Cjs)) {
+                error(node, Diagnostics.The_import_meta_meta_property_is_not_allowed_in_CommonJS_module_files);
+                Debug.assert(file.externalModuleIndicator === undefined, "Containing `.cjs` file should not be a module.");
+            }
+            else {
+                if (moduleKind !== ModuleKind.ESNext && moduleKind !== ModuleKind.System) {
+                    error(node, Diagnostics.The_import_meta_meta_property_is_only_allowed_when_the_module_option_is_esnext_or_system);
+                }
+                Debug.assert(!!file.externalModuleIndicator, "Containing file should be a module.");
+            }
             Debug.assert(!!(file.flags & NodeFlags.PossiblyContainsImportMeta), "Containing file is missing import meta node flag.");
-            Debug.assert(!!file.externalModuleIndicator, "Containing file should be a module.");
             return node.name.escapedText === "meta" ? getGlobalImportMetaType() : errorType;
         }
 
@@ -35466,7 +35472,8 @@ namespace ts {
         }
 
         function checkGrammarModuleElementContext(node: Statement, errorMessage: DiagnosticMessage): boolean {
-            const isInAppropriateContext = node.parent.kind === SyntaxKind.SourceFile || node.parent.kind === SyntaxKind.ModuleBlock || node.parent.kind === SyntaxKind.ModuleDeclaration;
+            const isInAppropriateContext = (node.parent.kind === SyntaxKind.SourceFile && !fileExtensionIs((<SourceFile>node.parent).fileName, Extension.Cjs))
+                || node.parent.kind === SyntaxKind.ModuleBlock || node.parent.kind === SyntaxKind.ModuleDeclaration;
             if (!isInAppropriateContext) {
                 grammarErrorOnFirstToken(node, errorMessage);
             }
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 82f3cb4ce579b..5ae62939a24d3 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -1180,6 +1180,10 @@
         "category": "Error",
         "code": 1388
     },
+    "The 'import.meta' meta-property is not allowed in CommonJS module files.": {
+        "category": "Error",
+        "code": 1389
+    },
 
     "The types of '{0}' are incompatible between these types.": {
         "category": "Error",
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index f976c38ea6af8..54ef9a6d29ca0 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -116,9 +116,11 @@ namespace ts {
             return Extension.Json;
         }
 
+        const { fileName } = sourceFile;
+
         if (options.jsx === JsxEmit.Preserve) {
             if (isSourceFileJS(sourceFile)) {
-                if (fileExtensionIs(sourceFile.fileName, Extension.Jsx)) {
+                if (fileExtensionIs(fileName, Extension.Jsx)) {
                     return Extension.Jsx;
                 }
             }
@@ -127,6 +129,16 @@ namespace ts {
                 return Extension.Jsx;
             }
         }
+
+        // Preserve the output extension for `.cjs` and `.mjs` files
+        if (fileExtensionIs(fileName, Extension.Cjs)) {
+            return Extension.Cjs;
+        }
+
+        if (fileExtensionIs(fileName, Extension.Mjs)) {
+            return Extension.Mjs;
+        }
+
         return Extension.Js;
     }
 
diff --git a/src/compiler/moduleNameResolver.ts b/src/compiler/moduleNameResolver.ts
index ad331c60be7f2..1610f2def199b 100644
--- a/src/compiler/moduleNameResolver.ts
+++ b/src/compiler/moduleNameResolver.ts
@@ -65,7 +65,7 @@ namespace ts {
      */
     enum Extensions {
         TypeScript, /** '.ts', '.tsx', or '.d.ts' */
-        JavaScript, /** '.js' or '.jsx' */
+        JavaScript, /** '.js', '.cjs', '.mjs' or '.jsx' */
         Json,       /** '.json' */
         TSConfig,   /** '.json' with `tsconfig` used instead of `index` */
         DtsOnly /** Only '.d.ts' */
@@ -1096,6 +1096,7 @@ namespace ts {
             case Extensions.TypeScript:
                 return tryExtension(Extension.Ts) || tryExtension(Extension.Tsx) || tryExtension(Extension.Dts);
             case Extensions.JavaScript:
+                // `.cjs` and `.mjs` file extensions must always have the file extension
                 return tryExtension(Extension.Js) || tryExtension(Extension.Jsx);
             case Extensions.TSConfig:
             case Extensions.Json:
@@ -1235,7 +1236,7 @@ namespace ts {
     function extensionIsOk(extensions: Extensions, extension: Extension): boolean {
         switch (extensions) {
             case Extensions.JavaScript:
-                return extension === Extension.Js || extension === Extension.Jsx;
+                return extension === Extension.Js || extension === Extension.Cjs || extension === Extension.Mjs || extension === Extension.Jsx;
             case Extensions.TSConfig:
             case Extensions.Json:
                 return extension === Extension.Json;
diff --git a/src/compiler/moduleSpecifiers.ts b/src/compiler/moduleSpecifiers.ts
index 54be63be022fa..edc94b7ff8ac0 100644
--- a/src/compiler/moduleSpecifiers.ts
+++ b/src/compiler/moduleSpecifiers.ts
@@ -17,6 +17,10 @@ namespace ts.moduleSpecifiers {
             ending: getEnding(),
         };
         function getEnding(): Ending {
+            // `.mjs` files must always use file extensions in import specifiers
+            if (fileExtensionIs(importingSourceFile.fileName, Extension.Mjs)) {
+                return Ending.JsExtension;
+            }
             switch (importModuleSpecifierEnding) {
                 case "minimal": return Ending.Minimal;
                 case "index": return Ending.Index;
@@ -309,6 +313,8 @@ namespace ts.moduleSpecifiers {
         const relativePath = normalizedSourcePath !== undefined ? ensurePathIsNonModuleName(getRelativePathFromDirectory(normalizedSourcePath, normalizedTargetPath, getCanonicalFileName)) : normalizedTargetPath;
         return getEmitModuleResolutionKind(compilerOptions) === ModuleResolutionKind.NodeJs
             ? removeExtensionAndIndexPostFix(relativePath, ending, compilerOptions)
+            // `.cjs` and `.mjs` files must always be imported with the file extension:
+            : fileExtensionIsOneOf(relativePath, [Extension.Cjs, Extension.Mjs]) ? relativePath
             : removeFileExtension(relativePath);
     }
 
@@ -490,7 +496,8 @@ namespace ts.moduleSpecifiers {
     }
 
     function removeExtensionAndIndexPostFix(fileName: string, ending: Ending, options: CompilerOptions): string {
-        if (fileExtensionIs(fileName, Extension.Json)) return fileName;
+        // `.cjs` and `.mjs` files must always be imported with the file extension, as Node doesn't resolve them by default:
+        if (fileExtensionIsOneOf(fileName, [Extension.Cjs, Extension.Mjs, Extension.Json])) return fileName;
         const noExtension = removeFileExtension(fileName);
         switch (ending) {
             case Ending.Minimal:
@@ -513,6 +520,8 @@ namespace ts.moduleSpecifiers {
             case Extension.Tsx:
                 return options.jsx === JsxEmit.Preserve ? Extension.Jsx : Extension.Js;
             case Extension.Js:
+            case Extension.Cjs:
+            case Extension.Mjs:
             case Extension.Jsx:
             case Extension.Json:
                 return ext;
diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 1729e3a810c4a..4cb6e485e1026 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -636,7 +636,11 @@ namespace ts {
 
     // See also `isExternalOrCommonJsModule` in utilities.ts
     export function isExternalModule(file: SourceFile): boolean {
-        return file.externalModuleIndicator !== undefined;
+        return file.externalModuleIndicator !== undefined || fileExtensionIs(file.fileName, Extension.Mjs);
+    }
+
+    export function isCommonJsModule(file: SourceFile): boolean {
+        return file.commonJsModuleIndicator !== undefined || fileExtensionIs(file.fileName, Extension.Cjs);
     }
 
     // Produces a new SourceFile for the 'newText' provided. The 'textChangeRange' parameter
@@ -1157,6 +1161,8 @@ namespace ts {
             // this is quite rare comparing to other nodes and createNode should be as fast as possible
             let sourceFile = factory.createSourceFile(statements, endOfFileToken, flags);
             setTextRangePosWidth(sourceFile, 0, sourceText.length);
+
+            sourceFile.fileName = fileName;
             setExternalModuleIndicator(sourceFile);
 
             // If we parsed this as an external module, it may contain top-level await
@@ -1168,7 +1174,6 @@ namespace ts {
             sourceFile.bindDiagnostics = [];
             sourceFile.bindSuggestionDiagnostics = undefined;
             sourceFile.languageVersion = languageVersion;
-            sourceFile.fileName = fileName;
             sourceFile.languageVariant = getLanguageVariant(scriptKind);
             sourceFile.isDeclarationFile = isDeclarationFile;
             sourceFile.scriptKind = scriptKind;
@@ -7047,6 +7052,9 @@ namespace ts {
         }
 
         function setExternalModuleIndicator(sourceFile: SourceFile) {
+            // `.cjs` files are never ECMAScript modules
+            if (fileExtensionIs(sourceFile.fileName, Extension.Cjs)) return;
+
             // Try to use the first top-level import/export when available, then
             // fall back to looking for an 'import.meta' somewhere in the tree if necessary.
             sourceFile.externalModuleIndicator =
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 87f4637258cb0..96ebc35745248 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -3119,7 +3119,10 @@ namespace ts {
 
             const languageVersion = options.target || ScriptTarget.ES3;
 
-            const firstNonAmbientExternalModuleSourceFile = find(files, f => isExternalModule(f) && !f.isDeclarationFile);
+            const firstNonAmbientExternalModuleSourceFile = find(files, f =>
+                // This can't use `isExternalModule(f)`, as that can return `.mjs` files that have an undefined `externalModuleIndicator`,
+                // and `firstNonAmbientExternalModuleSourceFile` is only used for `externalModuleIndicator`.
+                f.externalModuleIndicator !== undefined && !f.isDeclarationFile);
             if (options.isolatedModules) {
                 if (options.module === ModuleKind.None && languageVersion < ScriptTarget.ES2015) {
                     createDiagnosticForOptionName(Diagnostics.Option_isolatedModules_can_only_be_used_when_either_option_module_is_provided_or_option_target_is_ES2015_or_higher, "isolatedModules", "target");
@@ -3782,6 +3785,8 @@ namespace ts {
             case Extension.Jsx:
                 return needJsx() || needAllowJs();
             case Extension.Js:
+            case Extension.Cjs:
+            case Extension.Mjs:
                 return needAllowJs();
             case Extension.Json:
                 return needResolveJsonModule();
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 30a0dc4e7e952..2858631e42897 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -6176,6 +6176,8 @@ namespace ts {
         Tsx = ".tsx",
         Dts = ".d.ts",
         Js = ".js",
+        Cjs = ".cjs",
+        Mjs = ".mjs",
         Jsx = ".jsx",
         Json = ".json",
         TsBuildInfo = ".tsbuildinfo"
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index d7c00dbcc14c9..cc1e697132080 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -697,7 +697,7 @@ namespace ts {
     }
 
     export function isEffectiveExternalModule(node: SourceFile, compilerOptions: CompilerOptions) {
-        return isExternalModule(node) || compilerOptions.isolatedModules || ((getEmitModuleKind(compilerOptions) === ModuleKind.CommonJS) && !!node.commonJsModuleIndicator);
+        return isExternalModule(node) || compilerOptions.isolatedModules || ((getEmitModuleKind(compilerOptions) === ModuleKind.CommonJS) && isCommonJsModule(node));
     }
 
     /**
@@ -1023,7 +1023,7 @@ namespace ts {
     }
 
     export function isExternalOrCommonJsModule(file: SourceFile): boolean {
-        return (file.externalModuleIndicator || file.commonJsModuleIndicator) !== undefined;
+        return (file.externalModuleIndicator || file.commonJsModuleIndicator) !== undefined || fileExtensionIsOneOf(file.fileName || "", [Extension.Mjs, Extension.Cjs]);
     }
 
 
@@ -6325,6 +6325,8 @@ namespace ts {
         const ext = fileName.substr(fileName.lastIndexOf("."));
         switch (ext.toLowerCase()) {
             case Extension.Js:
+            case Extension.Cjs:
+            case Extension.Mjs:
                 return ScriptKind.JS;
             case Extension.Jsx:
                 return ScriptKind.JSX;
@@ -6346,8 +6348,8 @@ namespace ts {
     export const supportedTSExtensionsWithJson: readonly Extension[] = [Extension.Ts, Extension.Tsx, Extension.Dts, Extension.Json];
     /** Must have ".d.ts" first because if ".ts" goes first, that will be detected as the extension instead of ".d.ts". */
     export const supportedTSExtensionsForExtractExtension: readonly Extension[] = [Extension.Dts, Extension.Ts, Extension.Tsx];
-    export const supportedJSExtensions: readonly Extension[] = [Extension.Js, Extension.Jsx];
-    export const supportedJSAndJsonExtensions: readonly Extension[] = [Extension.Js, Extension.Jsx, Extension.Json];
+    export const supportedJSExtensions: readonly Extension[] = [Extension.Js, Extension.Jsx, Extension.Cjs, Extension.Mjs];
+    export const supportedJSAndJsonExtensions: readonly Extension[] = [Extension.Js, Extension.Jsx, Extension.Cjs, Extension.Mjs, Extension.Json];
     const allSupportedExtensions: readonly Extension[] = [...supportedTSExtensions, ...supportedJSExtensions];
     const allSupportedExtensionsWithJson: readonly Extension[] = [...supportedTSExtensions, ...supportedJSExtensions, Extension.Json];
 
@@ -6451,7 +6453,7 @@ namespace ts {
         }
     }
 
-    const extensionsToRemove = [Extension.Dts, Extension.Ts, Extension.Js, Extension.Tsx, Extension.Jsx, Extension.Json];
+    const extensionsToRemove = [Extension.Dts, Extension.Ts, Extension.Js, Extension.Cjs, Extension.Mjs, Extension.Tsx, Extension.Jsx, Extension.Json];
     export function removeFileExtension(path: string): string {
         for (const ext of extensionsToRemove) {
             const extensionless = tryRemoveExtension(path, ext);
diff --git a/src/services/codefixes/importFixes.ts b/src/services/codefixes/importFixes.ts
index 2adcba0a9eec0..e308d9fbf3b8b 100644
--- a/src/services/codefixes/importFixes.ts
+++ b/src/services/codefixes/importFixes.ts
@@ -363,9 +363,8 @@ namespace ts.codefix {
     }
 
     function shouldUseRequire(sourceFile: SourceFile, compilerOptions: CompilerOptions): boolean {
-        return isSourceFileJS(sourceFile)
-            && !sourceFile.externalModuleIndicator
-            && (!!sourceFile.commonJsModuleIndicator || getEmitModuleKind(compilerOptions) < ModuleKind.ES2015);
+        if (!isSourceFileJS(sourceFile) || isExternalModule(sourceFile)) return false;
+        return isCommonJsModule(sourceFile) || getEmitModuleKind(compilerOptions) < ModuleKind.ES2015;
     }
 
     function getNewImportInfos(
diff --git a/src/services/completions.ts b/src/services/completions.ts
index 67b9f0d94ce80..6db8c2d0c4fa8 100644
--- a/src/services/completions.ts
+++ b/src/services/completions.ts
@@ -1442,7 +1442,7 @@ namespace ts.Completions {
             // If not already a module, must have modules enabled.
             if (!preferences.includeCompletionsForModuleExports) return false;
             // If already using ES6 modules, OK to continue using them.
-            if (sourceFile.externalModuleIndicator || sourceFile.commonJsModuleIndicator) return true;
+            if (isExternalOrCommonJsModule(sourceFile)) return true;
             // If module transpilation is enabled or we're targeting es6 or above, or not emitting, OK.
             if (compilerOptionsIndicateEs6Modules(program.getCompilerOptions())) return true;
             // If some file is using ES6 modules, assume that it's OK to add more.
diff --git a/src/services/refactors/extractSymbol.ts b/src/services/refactors/extractSymbol.ts
index c2234a891dd67..79d78aec45870 100644
--- a/src/services/refactors/extractSymbol.ts
+++ b/src/services/refactors/extractSymbol.ts
@@ -481,7 +481,7 @@ namespace ts.refactor.extractSymbol {
                         // falls through
                     case SyntaxKind.ClassDeclaration:
                     case SyntaxKind.FunctionDeclaration:
-                        if (isSourceFile(node.parent) && node.parent.externalModuleIndicator === undefined) {
+                        if (isSourceFile(node.parent) && !isExternalModule(node.parent)) {
                             // You cannot extract global declarations
                             (errors || (errors = [] as Diagnostic[])).push(createDiagnosticForNode(node, Messages.functionWillNotBeVisibleInTheNewScope));
                         }
@@ -772,7 +772,7 @@ namespace ts.refactor.extractSymbol {
     function getDescriptionForModuleLikeDeclaration(scope: SourceFile | ModuleBlock): string | SpecialScope {
         return scope.kind === SyntaxKind.ModuleBlock
             ? `namespace '${scope.parent.name.getText()}'`
-            : scope.externalModuleIndicator ? SpecialScope.Module : SpecialScope.Global;
+            : isExternalModule(scope) ? SpecialScope.Module : SpecialScope.Global;
     }
 
     const enum SpecialScope {
diff --git a/src/services/refactors/moveToNewFile.ts b/src/services/refactors/moveToNewFile.ts
index fb151d6dba9f3..d1b9d8340d497 100644
--- a/src/services/refactors/moveToNewFile.ts
+++ b/src/services/refactors/moveToNewFile.ts
@@ -112,12 +112,12 @@ namespace ts.refactor {
     ) {
         const checker = program.getTypeChecker();
 
-        if (!oldFile.externalModuleIndicator && !oldFile.commonJsModuleIndicator) {
+        if (!isExternalOrCommonJsModule(oldFile)) {
             deleteMovedStatements(oldFile, toMove.ranges, changes);
             return toMove.all;
         }
 
-        const useEs6ModuleSyntax = !!oldFile.externalModuleIndicator;
+        const useEs6ModuleSyntax = isExternalModule(oldFile);
         const quotePreference = getQuotePreference(oldFile, preferences);
         const importsFromNewFile = createOldFileImportsFromNewFile(usage.oldFileImportsFromNewFile, newModuleName, useEs6ModuleSyntax, quotePreference);
         if (importsFromNewFile) {
diff --git a/src/services/stringCompletions.ts b/src/services/stringCompletions.ts
index c3473b6251eae..48ad2d3980dd0 100644
--- a/src/services/stringCompletions.ts
+++ b/src/services/stringCompletions.ts
@@ -84,6 +84,8 @@ namespace ts.Completions.StringCompletions {
         switch (extension) {
             case Extension.Dts: return ScriptElementKindModifier.dtsModifier;
             case Extension.Js: return ScriptElementKindModifier.jsModifier;
+            case Extension.Cjs: return ScriptElementKindModifier.cjsModifier;
+            case Extension.Mjs: return ScriptElementKindModifier.mjsModifier;
             case Extension.Json: return ScriptElementKindModifier.jsonModifier;
             case Extension.Jsx: return ScriptElementKindModifier.jsxModifier;
             case Extension.Ts: return ScriptElementKindModifier.tsModifier;
diff --git a/src/services/suggestionDiagnostics.ts b/src/services/suggestionDiagnostics.ts
index a8c50322522a1..580f82d10ce7f 100644
--- a/src/services/suggestionDiagnostics.ts
+++ b/src/services/suggestionDiagnostics.ts
@@ -8,6 +8,8 @@ namespace ts {
         const checker = program.getTypeChecker();
 
         if (sourceFile.commonJsModuleIndicator &&
+            // ES6 module syntax is illegal in `.cjs` files, which are always CommonJS files
+            !fileExtensionIs(sourceFile.fileName, Extension.Cjs) &&
             (programContainsEs6Modules(program) || compilerOptionsIndicateEs6Modules(program.getCompilerOptions())) &&
             containsTopLevelCommonjs(sourceFile)) {
             diags.push(createDiagnosticForNode(getErrorNodeFromCommonJsIndicator(sourceFile.commonJsModuleIndicator), Diagnostics.File_is_a_CommonJS_module_it_may_be_converted_to_an_ES6_module));
diff --git a/src/services/types.ts b/src/services/types.ts
index 0ebd80372cbea..1f18f3795cb8c 100644
--- a/src/services/types.ts
+++ b/src/services/types.ts
@@ -1337,6 +1337,8 @@ namespace ts {
         dtsModifier = ".d.ts",
         tsModifier = ".ts",
         tsxModifier = ".tsx",
+        cjsModifier = ".cjs",
+        mjsModifier = ".mjs",
         jsModifier = ".js",
         jsxModifier = ".jsx",
         jsonModifier = ".json",
diff --git a/src/services/utilities.ts b/src/services/utilities.ts
index c11c65d076dd6..bab3b2039caf3 100644
--- a/src/services/utilities.ts
+++ b/src/services/utilities.ts
@@ -1743,10 +1743,10 @@ namespace ts {
     }
 
     export function programContainsModules(program: Program): boolean {
-        return program.getSourceFiles().some(s => !s.isDeclarationFile && !program.isSourceFileFromExternalLibrary(s) && !!(s.externalModuleIndicator || s.commonJsModuleIndicator));
+        return program.getSourceFiles().some(s => !s.isDeclarationFile && !program.isSourceFileFromExternalLibrary(s) && isExternalOrCommonJsModule(s));
     }
     export function programContainsEs6Modules(program: Program): boolean {
-        return program.getSourceFiles().some(s => !s.isDeclarationFile && !program.isSourceFileFromExternalLibrary(s) && !!s.externalModuleIndicator);
+        return program.getSourceFiles().some(s => !s.isDeclarationFile && !program.isSourceFileFromExternalLibrary(s) && isExternalModule(s));
     }
     export function compilerOptionsIndicateEs6Modules(compilerOptions: CompilerOptions): boolean {
         return !!compilerOptions.module || compilerOptions.target! >= ScriptTarget.ES2015 || !!compilerOptions.noEmit;
@@ -2924,7 +2924,7 @@ namespace ts {
     export function isNonGlobalDeclaration(declaration: Declaration) {
         const sourceFile = declaration.getSourceFile();
         // If the file is not a module, the declaration is global
-        if (!sourceFile.externalModuleIndicator && !sourceFile.commonJsModuleIndicator) {
+        if (!isExternalOrCommonJsModule(sourceFile)) {
             return false;
         }
         // If the file is a module written in TypeScript, it still might be in a `declare global` augmentation
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
index 5a803b4c659ed..943ea8ed66e25 100644
--- a/tests/baselines/reference/api/tsserverlibrary.d.ts
+++ b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -3006,6 +3006,8 @@ declare namespace ts {
         Tsx = ".tsx",
         Dts = ".d.ts",
         Js = ".js",
+        Cjs = ".cjs",
+        Mjs = ".mjs",
         Jsx = ".jsx",
         Json = ".json",
         TsBuildInfo = ".tsbuildinfo"
@@ -4481,6 +4483,7 @@ declare namespace ts {
      */
     export function parseJsonText(fileName: string, sourceText: string): JsonSourceFile;
     export function isExternalModule(file: SourceFile): boolean;
+    export function isCommonJsModule(file: SourceFile): boolean;
     export function updateSourceFile(sourceFile: SourceFile, newText: string, textChangeRange: TextChangeRange, aggressiveChecks?: boolean): SourceFile;
     export {};
 }
@@ -6162,6 +6165,8 @@ declare namespace ts {
         dtsModifier = ".d.ts",
         tsModifier = ".ts",
         tsxModifier = ".tsx",
+        cjsModifier = ".cjs",
+        mjsModifier = ".mjs",
         jsModifier = ".js",
         jsxModifier = ".jsx",
         jsonModifier = ".json"
diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
index bb9aa1f2d2537..6868c7f4b35d4 100644
--- a/tests/baselines/reference/api/typescript.d.ts
+++ b/tests/baselines/reference/api/typescript.d.ts
@@ -3006,6 +3006,8 @@ declare namespace ts {
         Tsx = ".tsx",
         Dts = ".d.ts",
         Js = ".js",
+        Cjs = ".cjs",
+        Mjs = ".mjs",
         Jsx = ".jsx",
         Json = ".json",
         TsBuildInfo = ".tsbuildinfo"
@@ -4481,6 +4483,7 @@ declare namespace ts {
      */
     export function parseJsonText(fileName: string, sourceText: string): JsonSourceFile;
     export function isExternalModule(file: SourceFile): boolean;
+    export function isCommonJsModule(file: SourceFile): boolean;
     export function updateSourceFile(sourceFile: SourceFile, newText: string, textChangeRange: TextChangeRange, aggressiveChecks?: boolean): SourceFile;
     export {};
 }
@@ -6162,6 +6165,8 @@ declare namespace ts {
         dtsModifier = ".d.ts",
         tsModifier = ".ts",
         tsxModifier = ".tsx",
+        cjsModifier = ".cjs",
+        mjsModifier = ".mjs",
         jsModifier = ".js",
         jsxModifier = ".jsx",
         jsonModifier = ".json"
diff --git a/tests/baselines/reference/declarationEmitInvalidReferenceAllowJs.errors.txt b/tests/baselines/reference/declarationEmitInvalidReferenceAllowJs.errors.txt
index 79f9afa5f34cb..5caaa4a8aedb6 100644
--- a/tests/baselines/reference/declarationEmitInvalidReferenceAllowJs.errors.txt
+++ b/tests/baselines/reference/declarationEmitInvalidReferenceAllowJs.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/compiler/declarationEmitInvalidReferenceAllowJs.ts(1,22): error TS6231: Could not resolve the path 'tests/cases/compiler/invalid' with the extensions: '.ts', '.tsx', '.d.ts', '.js', '.jsx'.
+tests/cases/compiler/declarationEmitInvalidReferenceAllowJs.ts(1,22): error TS6231: Could not resolve the path 'tests/cases/compiler/invalid' with the extensions: '.ts', '.tsx', '.d.ts', '.js', '.jsx', '.cjs', '.mjs'.
 
 
 ==== tests/cases/compiler/declarationEmitInvalidReferenceAllowJs.ts (1 errors) ====
     /// <reference path="invalid" />
                          ~~~~~~~
-!!! error TS6231: Could not resolve the path 'tests/cases/compiler/invalid' with the extensions: '.ts', '.tsx', '.d.ts', '.js', '.jsx'.
+!!! error TS6231: Could not resolve the path 'tests/cases/compiler/invalid' with the extensions: '.ts', '.tsx', '.d.ts', '.js', '.jsx', '.cjs', '.mjs'.
     var x = 0; 
     
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilationWithMapFileAsJs.errors.txt b/tests/baselines/reference/jsFileCompilationWithMapFileAsJs.errors.txt
index 4dced529edf10..4ef8f6c524f95 100644
--- a/tests/baselines/reference/jsFileCompilationWithMapFileAsJs.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationWithMapFileAsJs.errors.txt
@@ -1,11 +1,11 @@
 error TS5055: Cannot write file 'tests/cases/compiler/b.js' because it would overwrite input file.
   Adding a tsconfig.json file will help organize projects that contain both TypeScript and JavaScript files. Learn more at https://aka.ms/tsconfig.
-error TS6054: File 'tests/cases/compiler/b.js.map' has an unsupported extension. The only supported extensions are '.ts', '.tsx', '.d.ts', '.js', '.jsx'.
+error TS6054: File 'tests/cases/compiler/b.js.map' has an unsupported extension. The only supported extensions are '.ts', '.tsx', '.d.ts', '.js', '.jsx', '.cjs', '.mjs'.
 
 
 !!! error TS5055: Cannot write file 'tests/cases/compiler/b.js' because it would overwrite input file.
 !!! error TS5055:   Adding a tsconfig.json file will help organize projects that contain both TypeScript and JavaScript files. Learn more at https://aka.ms/tsconfig.
-!!! error TS6054: File 'tests/cases/compiler/b.js.map' has an unsupported extension. The only supported extensions are '.ts', '.tsx', '.d.ts', '.js', '.jsx'.
+!!! error TS6054: File 'tests/cases/compiler/b.js.map' has an unsupported extension. The only supported extensions are '.ts', '.tsx', '.d.ts', '.js', '.jsx', '.cjs', '.mjs'.
 ==== tests/cases/compiler/a.ts (0 errors) ====
     class c {
     }
diff --git a/tests/baselines/reference/jsFileCompilationWithMapFileAsJsWithInlineSourceMap.errors.txt b/tests/baselines/reference/jsFileCompilationWithMapFileAsJsWithInlineSourceMap.errors.txt
index 4dced529edf10..4ef8f6c524f95 100644
--- a/tests/baselines/reference/jsFileCompilationWithMapFileAsJsWithInlineSourceMap.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationWithMapFileAsJsWithInlineSourceMap.errors.txt
@@ -1,11 +1,11 @@
 error TS5055: Cannot write file 'tests/cases/compiler/b.js' because it would overwrite input file.
   Adding a tsconfig.json file will help organize projects that contain both TypeScript and JavaScript files. Learn more at https://aka.ms/tsconfig.
-error TS6054: File 'tests/cases/compiler/b.js.map' has an unsupported extension. The only supported extensions are '.ts', '.tsx', '.d.ts', '.js', '.jsx'.
+error TS6054: File 'tests/cases/compiler/b.js.map' has an unsupported extension. The only supported extensions are '.ts', '.tsx', '.d.ts', '.js', '.jsx', '.cjs', '.mjs'.
 
 
 !!! error TS5055: Cannot write file 'tests/cases/compiler/b.js' because it would overwrite input file.
 !!! error TS5055:   Adding a tsconfig.json file will help organize projects that contain both TypeScript and JavaScript files. Learn more at https://aka.ms/tsconfig.
-!!! error TS6054: File 'tests/cases/compiler/b.js.map' has an unsupported extension. The only supported extensions are '.ts', '.tsx', '.d.ts', '.js', '.jsx'.
+!!! error TS6054: File 'tests/cases/compiler/b.js.map' has an unsupported extension. The only supported extensions are '.ts', '.tsx', '.d.ts', '.js', '.jsx', '.cjs', '.mjs'.
 ==== tests/cases/compiler/a.ts (0 errors) ====
     class c {
     }
diff --git a/tests/baselines/reference/jsFileCompilation_cjs.errors.txt b/tests/baselines/reference/jsFileCompilation_cjs.errors.txt
new file mode 100644
index 0000000000000..de46607d7c081
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_cjs.errors.txt
@@ -0,0 +1,29 @@
+tests/cases/compiler/a.cjs(1,1): error TS1233: An export declaration can only be used in a module.
+tests/cases/compiler/a.cjs(2,1): error TS1389: The 'import.meta' meta-property is not allowed in CommonJS module files.
+tests/cases/compiler/c.cjs(4,7): error TS1210: Invalid use of 'eval'. Class definitions are automatically in strict mode.
+tests/cases/compiler/c.cjs(7,13): error TS1213: Identifier expected. 'let' is a reserved word in strict mode. Class definitions are automatically in strict mode.
+
+
+==== tests/cases/compiler/a.cjs (2 errors) ====
+    export {}; // error
+    ~~~~~~
+!!! error TS1233: An export declaration can only be used in a module.
+    import.meta; // error
+    ~~~~~~~~~~~
+!!! error TS1389: The 'import.meta' meta-property is not allowed in CommonJS module files.
+    
+==== tests/cases/compiler/c.cjs (2 errors) ====
+    // this is not in strict mode but class definitions are always in strict mode
+    
+    class c {
+        a(eval) { //error
+          ~~~~
+!!! error TS1210: Invalid use of 'eval'. Class definitions are automatically in strict mode.
+        }
+        method() {
+            var let = 10; // error
+                ~~~
+!!! error TS1213: Identifier expected. 'let' is a reserved word in strict mode. Class definitions are automatically in strict mode.
+        }
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilation_cjs.symbols b/tests/baselines/reference/jsFileCompilation_cjs.symbols
new file mode 100644
index 0000000000000..84bd9cc9d5ebb
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_cjs.symbols
@@ -0,0 +1,22 @@
+=== tests/cases/compiler/a.cjs ===
+export {}; // error
+No type information for this code.import.meta; // error
+No type information for this code.
+No type information for this code.=== tests/cases/compiler/c.cjs ===
+// this is not in strict mode but class definitions are always in strict mode
+
+class c {
+>c : Symbol(c, Decl(c.cjs, 0, 0))
+
+    a(eval) { //error
+>a : Symbol(c.a, Decl(c.cjs, 2, 9))
+>eval : Symbol(eval, Decl(c.cjs, 3, 6))
+    }
+    method() {
+>method : Symbol(c.method, Decl(c.cjs, 4, 5))
+
+        var let = 10; // error
+>let : Symbol(let, Decl(c.cjs, 6, 11))
+    }
+}
+
diff --git a/tests/baselines/reference/jsFileCompilation_cjs.types b/tests/baselines/reference/jsFileCompilation_cjs.types
new file mode 100644
index 0000000000000..ba8d39924c75a
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_cjs.types
@@ -0,0 +1,25 @@
+=== tests/cases/compiler/a.cjs ===
+export {}; // error
+import.meta; // error
+>import.meta : ImportMeta
+>meta : any
+
+=== tests/cases/compiler/c.cjs ===
+// this is not in strict mode but class definitions are always in strict mode
+
+class c {
+>c : c
+
+    a(eval) { //error
+>a : (eval: any) => void
+>eval : any
+    }
+    method() {
+>method : () => void
+
+        var let = 10; // error
+>let : number
+>10 : 10
+    }
+}
+
diff --git a/tests/baselines/reference/jsFileCompilation_cjs_importMissingFileExtension_cjs_mjs.errors.txt b/tests/baselines/reference/jsFileCompilation_cjs_importMissingFileExtension_cjs_mjs.errors.txt
new file mode 100644
index 0000000000000..da6db8c4ec38c
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_cjs_importMissingFileExtension_cjs_mjs.errors.txt
@@ -0,0 +1,20 @@
+tests/cases/compiler/index.cjs(1,22): error TS2792: Cannot find module './blah'. Did you mean to set the 'moduleResolution' option to 'node', or to add aliases to the 'paths' option?
+tests/cases/compiler/index.cjs(2,34): error TS2792: Cannot find module './utils'. Did you mean to set the 'moduleResolution' option to 'node', or to add aliases to the 'paths' option?
+
+
+==== tests/cases/compiler/index.cjs (2 errors) ====
+    const Blah = require("./blah");
+                         ~~~~~~~~
+!!! error TS2792: Cannot find module './blah'. Did you mean to set the 'moduleResolution' option to 'node', or to add aliases to the 'paths' option?
+    const { util1, util2 } = require("./utils");
+                                     ~~~~~~~~~
+!!! error TS2792: Cannot find module './utils'. Did you mean to set the 'moduleResolution' option to 'node', or to add aliases to the 'paths' option?
+    
+==== tests/cases/compiler/blah.mjs (0 errors) ====
+    export default class Blah {}
+    
+==== tests/cases/compiler/utils.cjs (0 errors) ====
+    function util1() {}
+    function util2() {}
+    module.exports = { util1, util2 };
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilation_cjs_importMissingFileExtension_cjs_mjs.symbols b/tests/baselines/reference/jsFileCompilation_cjs_importMissingFileExtension_cjs_mjs.symbols
new file mode 100644
index 0000000000000..06707917e1239
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_cjs_importMissingFileExtension_cjs_mjs.symbols
@@ -0,0 +1,10 @@
+=== tests/cases/compiler/index.cjs ===
+const Blah = require("./blah");
+>Blah : Symbol(Blah, Decl(index.cjs, 0, 5))
+>require : Symbol(require)
+
+const { util1, util2 } = require("./utils");
+>util1 : Symbol(util1, Decl(index.cjs, 1, 7))
+>util2 : Symbol(util2, Decl(index.cjs, 1, 14))
+>require : Symbol(require)
+
diff --git a/tests/baselines/reference/jsFileCompilation_cjs_importMissingFileExtension_cjs_mjs.types b/tests/baselines/reference/jsFileCompilation_cjs_importMissingFileExtension_cjs_mjs.types
new file mode 100644
index 0000000000000..6f23e94ea5b51
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_cjs_importMissingFileExtension_cjs_mjs.types
@@ -0,0 +1,14 @@
+=== tests/cases/compiler/index.cjs ===
+const Blah = require("./blah");
+>Blah : any
+>require("./blah") : any
+>require : any
+>"./blah" : "./blah"
+
+const { util1, util2 } = require("./utils");
+>util1 : any
+>util2 : any
+>require("./utils") : any
+>require : any
+>"./utils" : "./utils"
+
diff --git a/tests/baselines/reference/jsFileCompilation_js_importMissingFileExtension_cjs_mjs.errors.txt b/tests/baselines/reference/jsFileCompilation_js_importMissingFileExtension_cjs_mjs.errors.txt
new file mode 100644
index 0000000000000..395c8552d90d5
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_js_importMissingFileExtension_cjs_mjs.errors.txt
@@ -0,0 +1,20 @@
+tests/cases/compiler/index.js(1,18): error TS2792: Cannot find module './blah'. Did you mean to set the 'moduleResolution' option to 'node', or to add aliases to the 'paths' option?
+tests/cases/compiler/index.js(2,30): error TS2792: Cannot find module './utils'. Did you mean to set the 'moduleResolution' option to 'node', or to add aliases to the 'paths' option?
+
+
+==== tests/cases/compiler/blah.mjs (0 errors) ====
+    export default class Blah {}
+    
+==== tests/cases/compiler/utils.cjs (0 errors) ====
+    function util1() {}
+    function util2() {}
+    module.exports = { util1, util2 };
+    
+==== tests/cases/compiler/index.js (2 errors) ====
+    import Blah from "./blah";
+                     ~~~~~~~~
+!!! error TS2792: Cannot find module './blah'. Did you mean to set the 'moduleResolution' option to 'node', or to add aliases to the 'paths' option?
+    import { util1, util2 } from "./utils";
+                                 ~~~~~~~~~
+!!! error TS2792: Cannot find module './utils'. Did you mean to set the 'moduleResolution' option to 'node', or to add aliases to the 'paths' option?
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilation_js_importMissingFileExtension_cjs_mjs.symbols b/tests/baselines/reference/jsFileCompilation_js_importMissingFileExtension_cjs_mjs.symbols
new file mode 100644
index 0000000000000..9e1ba6c0b4e15
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_js_importMissingFileExtension_cjs_mjs.symbols
@@ -0,0 +1,26 @@
+=== tests/cases/compiler/blah.mjs ===
+export default class Blah {}
+>Blah : Symbol(Blah, Decl(blah.mjs, 0, 0))
+
+=== tests/cases/compiler/utils.cjs ===
+function util1() {}
+>util1 : Symbol(util1, Decl(utils.cjs, 0, 0))
+
+function util2() {}
+>util2 : Symbol(util2, Decl(utils.cjs, 0, 19))
+
+module.exports = { util1, util2 };
+>module.exports : Symbol("tests/cases/compiler/utils", Decl(utils.cjs, 0, 0))
+>module : Symbol(export=, Decl(utils.cjs, 1, 19))
+>exports : Symbol(export=, Decl(utils.cjs, 1, 19))
+>util1 : Symbol(util1, Decl(utils.cjs, 2, 18))
+>util2 : Symbol(util2, Decl(utils.cjs, 2, 25))
+
+=== tests/cases/compiler/index.js ===
+import Blah from "./blah";
+>Blah : Symbol(Blah, Decl(index.js, 0, 6))
+
+import { util1, util2 } from "./utils";
+>util1 : Symbol(util1, Decl(index.js, 1, 8))
+>util2 : Symbol(util2, Decl(index.js, 1, 15))
+
diff --git a/tests/baselines/reference/jsFileCompilation_js_importMissingFileExtension_cjs_mjs.types b/tests/baselines/reference/jsFileCompilation_js_importMissingFileExtension_cjs_mjs.types
new file mode 100644
index 0000000000000..fc323eefacabd
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_js_importMissingFileExtension_cjs_mjs.types
@@ -0,0 +1,28 @@
+=== tests/cases/compiler/blah.mjs ===
+export default class Blah {}
+>Blah : Blah
+
+=== tests/cases/compiler/utils.cjs ===
+function util1() {}
+>util1 : () => void
+
+function util2() {}
+>util2 : () => void
+
+module.exports = { util1, util2 };
+>module.exports = { util1, util2 } : { util1: () => void; util2: () => void; }
+>module.exports : { util1: () => void; util2: () => void; }
+>module : { "\"tests/cases/compiler/utils\"": { util1: () => void; util2: () => void; }; }
+>exports : { util1: () => void; util2: () => void; }
+>{ util1, util2 } : { util1: () => void; util2: () => void; }
+>util1 : () => void
+>util2 : () => void
+
+=== tests/cases/compiler/index.js ===
+import Blah from "./blah";
+>Blah : any
+
+import { util1, util2 } from "./utils";
+>util1 : any
+>util2 : any
+
diff --git a/tests/baselines/reference/jsFileCompilation_mjs.errors.txt b/tests/baselines/reference/jsFileCompilation_mjs.errors.txt
new file mode 100644
index 0000000000000..f2b33f25a63b6
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_mjs.errors.txt
@@ -0,0 +1,84 @@
+tests/cases/compiler/a.mjs(6,5): error TS1117: An object literal cannot have multiple properties with the same name in strict mode.
+tests/cases/compiler/a.mjs(6,5): error TS2300: Duplicate identifier 'a'.
+tests/cases/compiler/a.mjs(8,5): error TS1214: Identifier expected. 'let' is a reserved word in strict mode. Modules are automatically in strict mode.
+tests/cases/compiler/a.mjs(9,8): error TS1102: 'delete' cannot be called on an identifier in strict mode.
+tests/cases/compiler/a.mjs(9,8): error TS2703: The operand of a 'delete' operator must be a property reference.
+tests/cases/compiler/a.mjs(11,10): error TS1215: Invalid use of 'eval'. Modules are automatically in strict mode.
+tests/cases/compiler/a.mjs(13,10): error TS1215: Invalid use of 'arguments'. Modules are automatically in strict mode.
+tests/cases/compiler/a.mjs(16,1): error TS1101: 'with' statements are not allowed in strict mode.
+tests/cases/compiler/a.mjs(16,1): error TS2410: The 'with' statement is not supported. All symbols in a 'with' block will have type 'any'.
+tests/cases/compiler/b.mjs(2,7): error TS1210: Invalid use of 'eval'. Class definitions are automatically in strict mode.
+tests/cases/compiler/b.mjs(5,13): error TS1213: Identifier expected. 'let' is a reserved word in strict mode. Class definitions are automatically in strict mode.
+tests/cases/compiler/c.mjs(1,5): error TS1214: Identifier expected. 'let' is a reserved word in strict mode. Modules are automatically in strict mode.
+tests/cases/compiler/c.mjs(2,5): error TS1215: Invalid use of 'eval'. Modules are automatically in strict mode.
+tests/cases/compiler/d.mjs(1,9): error TS1121: Octal literals are not allowed in strict mode.
+tests/cases/compiler/d.mjs(1,11): error TS1005: ',' expected.
+
+
+==== tests/cases/compiler/a.mjs (9 errors) ====
+    // `.mjs` files are automatically external modules, and thus in strict mode
+    
+    var a = {
+        a: "hello", // error
+        b: 10,
+        a: 10 // error
+        ~
+!!! error TS1117: An object literal cannot have multiple properties with the same name in strict mode.
+        ~
+!!! error TS2300: Duplicate identifier 'a'.
+    };
+    var let = 10; // error
+        ~~~
+!!! error TS1214: Identifier expected. 'let' is a reserved word in strict mode. Modules are automatically in strict mode.
+    delete a; // error
+           ~
+!!! error TS1102: 'delete' cannot be called on an identifier in strict mode.
+           ~
+!!! error TS2703: The operand of a 'delete' operator must be a property reference.
+    try {
+    } catch (eval) { // error
+             ~~~~
+!!! error TS1215: Invalid use of 'eval'. Modules are automatically in strict mode.
+    }
+    function arguments() { // error
+             ~~~~~~~~~
+!!! error TS1215: Invalid use of 'arguments'. Modules are automatically in strict mode.
+    }
+    
+    with (a) {
+    ~~~~
+!!! error TS1101: 'with' statements are not allowed in strict mode.
+    ~~~~~~~~
+!!! error TS2410: The 'with' statement is not supported. All symbols in a 'with' block will have type 'any'.
+        b = 10;
+    }
+    
+==== tests/cases/compiler/b.mjs (2 errors) ====
+    class c {
+        a(eval) { //error
+          ~~~~
+!!! error TS1210: Invalid use of 'eval'. Class definitions are automatically in strict mode.
+        }
+        method() {
+            var let = 10; // error
+                ~~~
+!!! error TS1213: Identifier expected. 'let' is a reserved word in strict mode. Class definitions are automatically in strict mode.
+        }
+    }
+    
+==== tests/cases/compiler/c.mjs (2 errors) ====
+    var let = 10;
+        ~~~
+!!! error TS1214: Identifier expected. 'let' is a reserved word in strict mode. Modules are automatically in strict mode.
+    var eval = function () {
+        ~~~~
+!!! error TS1215: Invalid use of 'eval'. Modules are automatically in strict mode.
+    };
+    
+==== tests/cases/compiler/d.mjs (2 errors) ====
+    var x = 009; // error
+            ~~
+!!! error TS1121: Octal literals are not allowed in strict mode.
+              ~
+!!! error TS1005: ',' expected.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilation_mjs.symbols b/tests/baselines/reference/jsFileCompilation_mjs.symbols
new file mode 100644
index 0000000000000..229da71ad7aec
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_mjs.symbols
@@ -0,0 +1,65 @@
+=== tests/cases/compiler/a.mjs ===
+// `.mjs` files are automatically external modules, and thus in strict mode
+
+var a = {
+>a : Symbol(a, Decl(a.mjs, 2, 3))
+
+    a: "hello", // error
+>a : Symbol(a, Decl(a.mjs, 2, 9), Decl(a.mjs, 4, 10))
+
+    b: 10,
+>b : Symbol(b, Decl(a.mjs, 3, 15))
+
+    a: 10 // error
+>a : Symbol(a, Decl(a.mjs, 2, 9), Decl(a.mjs, 4, 10))
+
+};
+var let = 10; // error
+>let : Symbol(let, Decl(a.mjs, 7, 3))
+
+delete a; // error
+>a : Symbol(a, Decl(a.mjs, 2, 3))
+
+try {
+} catch (eval) { // error
+>eval : Symbol(eval, Decl(a.mjs, 10, 9))
+}
+function arguments() { // error
+>arguments : Symbol(arguments, Decl(a.mjs, 11, 1))
+}
+
+with (a) {
+>a : Symbol(a, Decl(a.mjs, 2, 3))
+
+    b = 10;
+}
+
+=== tests/cases/compiler/b.mjs ===
+class c {
+>c : Symbol(c, Decl(b.mjs, 0, 0))
+
+    a(eval) { //error
+>a : Symbol(c.a, Decl(b.mjs, 0, 9))
+>eval : Symbol(eval, Decl(b.mjs, 1, 6))
+    }
+    method() {
+>method : Symbol(c.method, Decl(b.mjs, 2, 5))
+
+        var let = 10; // error
+>let : Symbol(let, Decl(b.mjs, 4, 11))
+    }
+}
+
+=== tests/cases/compiler/c.mjs ===
+var let = 10;
+>let : Symbol(let, Decl(c.mjs, 0, 3))
+
+var eval = function () {
+>eval : Symbol(eval, Decl(c.mjs, 1, 3))
+
+};
+
+=== tests/cases/compiler/d.mjs ===
+var x = 009; // error
+>x : Symbol(x, Decl(d.mjs, 0, 3))
+
diff --git a/tests/baselines/reference/jsFileCompilation_mjs.types b/tests/baselines/reference/jsFileCompilation_mjs.types
new file mode 100644
index 0000000000000..5e81cbfd3a37b
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_mjs.types
@@ -0,0 +1,79 @@
+=== tests/cases/compiler/a.mjs ===
+// `.mjs` files are automatically external modules, and thus in strict mode
+
+var a = {
+>a : { a: number; b: number; }
+>{    a: "hello", // error    b: 10,    a: 10 // error} : { a: number; b: number; }
+
+    a: "hello", // error
+>a : string
+>"hello" : "hello"
+
+    b: 10,
+>b : number
+>10 : 10
+
+    a: 10 // error
+>a : string
+>10 : 10
+
+};
+var let = 10; // error
+>let : number
+>10 : 10
+
+delete a; // error
+>delete a : boolean
+>a : { a: number; b: number; }
+
+try {
+} catch (eval) { // error
+>eval : any
+}
+function arguments() { // error
+>arguments : () => void
+}
+
+with (a) {
+>a : { a: number; b: number; }
+
+    b = 10;
+>b = 10 : any
+>b : any
+>10 : any
+}
+
+=== tests/cases/compiler/b.mjs ===
+class c {
+>c : c
+
+    a(eval) { //error
+>a : (eval: any) => void
+>eval : any
+    }
+    method() {
+>method : () => void
+
+        var let = 10; // error
+>let : number
+>10 : 10
+    }
+}
+
+=== tests/cases/compiler/c.mjs ===
+var let = 10;
+>let : number
+>10 : 10
+
+var eval = function () {
+>eval : () => void
+>function () {} : () => void
+
+};
+
+=== tests/cases/compiler/d.mjs ===
+var x = 009; // error
+>x : number
+>00 : 0
+>9 : 9
+
diff --git a/tests/baselines/reference/jsFileCompilation_mjs_importMissingFileExtension_cjs_mjs.errors.txt b/tests/baselines/reference/jsFileCompilation_mjs_importMissingFileExtension_cjs_mjs.errors.txt
new file mode 100644
index 0000000000000..3219bb96545a8
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_mjs_importMissingFileExtension_cjs_mjs.errors.txt
@@ -0,0 +1,20 @@
+tests/cases/compiler/index.mjs(1,18): error TS2792: Cannot find module './blah'. Did you mean to set the 'moduleResolution' option to 'node', or to add aliases to the 'paths' option?
+tests/cases/compiler/index.mjs(2,30): error TS2792: Cannot find module './utils'. Did you mean to set the 'moduleResolution' option to 'node', or to add aliases to the 'paths' option?
+
+
+==== tests/cases/compiler/blah.mjs (0 errors) ====
+    export default class Blah {}
+    
+==== tests/cases/compiler/utils.cjs (0 errors) ====
+    function util1() {}
+    function util2() {}
+    module.exports = { util1, util2 };
+    
+==== tests/cases/compiler/index.mjs (2 errors) ====
+    import Blah from "./blah";
+                     ~~~~~~~~
+!!! error TS2792: Cannot find module './blah'. Did you mean to set the 'moduleResolution' option to 'node', or to add aliases to the 'paths' option?
+    import { util1, util2 } from "./utils";
+                                 ~~~~~~~~~
+!!! error TS2792: Cannot find module './utils'. Did you mean to set the 'moduleResolution' option to 'node', or to add aliases to the 'paths' option?
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilation_mjs_importMissingFileExtension_cjs_mjs.symbols b/tests/baselines/reference/jsFileCompilation_mjs_importMissingFileExtension_cjs_mjs.symbols
new file mode 100644
index 0000000000000..039028c31beb2
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_mjs_importMissingFileExtension_cjs_mjs.symbols
@@ -0,0 +1,26 @@
+=== tests/cases/compiler/blah.mjs ===
+export default class Blah {}
+>Blah : Symbol(Blah, Decl(blah.mjs, 0, 0))
+
+=== tests/cases/compiler/utils.cjs ===
+function util1() {}
+>util1 : Symbol(util1, Decl(utils.cjs, 0, 0))
+
+function util2() {}
+>util2 : Symbol(util2, Decl(utils.cjs, 0, 19))
+
+module.exports = { util1, util2 };
+>module.exports : Symbol("tests/cases/compiler/utils", Decl(utils.cjs, 0, 0))
+>module : Symbol(export=, Decl(utils.cjs, 1, 19))
+>exports : Symbol(export=, Decl(utils.cjs, 1, 19))
+>util1 : Symbol(util1, Decl(utils.cjs, 2, 18))
+>util2 : Symbol(util2, Decl(utils.cjs, 2, 25))
+
+=== tests/cases/compiler/index.mjs ===
+import Blah from "./blah";
+>Blah : Symbol(Blah, Decl(index.mjs, 0, 6))
+
+import { util1, util2 } from "./utils";
+>util1 : Symbol(util1, Decl(index.mjs, 1, 8))
+>util2 : Symbol(util2, Decl(index.mjs, 1, 15))
+
diff --git a/tests/baselines/reference/jsFileCompilation_mjs_importMissingFileExtension_cjs_mjs.types b/tests/baselines/reference/jsFileCompilation_mjs_importMissingFileExtension_cjs_mjs.types
new file mode 100644
index 0000000000000..3a1ffc5890808
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_mjs_importMissingFileExtension_cjs_mjs.types
@@ -0,0 +1,28 @@
+=== tests/cases/compiler/blah.mjs ===
+export default class Blah {}
+>Blah : Blah
+
+=== tests/cases/compiler/utils.cjs ===
+function util1() {}
+>util1 : () => void
+
+function util2() {}
+>util2 : () => void
+
+module.exports = { util1, util2 };
+>module.exports = { util1, util2 } : { util1: () => void; util2: () => void; }
+>module.exports : { util1: () => void; util2: () => void; }
+>module : { "\"tests/cases/compiler/utils\"": { util1: () => void; util2: () => void; }; }
+>exports : { util1: () => void; util2: () => void; }
+>{ util1, util2 } : { util1: () => void; util2: () => void; }
+>util1 : () => void
+>util2 : () => void
+
+=== tests/cases/compiler/index.mjs ===
+import Blah from "./blah";
+>Blah : any
+
+import { util1, util2 } from "./utils";
+>util1 : any
+>util2 : any
+
diff --git a/tests/baselines/reference/jsFileCompilation_node_cjs_importMissingFileExtension_cjs_mjs.errors.txt b/tests/baselines/reference/jsFileCompilation_node_cjs_importMissingFileExtension_cjs_mjs.errors.txt
new file mode 100644
index 0000000000000..e21cbb16ad426
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_node_cjs_importMissingFileExtension_cjs_mjs.errors.txt
@@ -0,0 +1,20 @@
+tests/cases/compiler/index.cjs(1,22): error TS2307: Cannot find module './blah' or its corresponding type declarations.
+tests/cases/compiler/index.cjs(2,34): error TS2307: Cannot find module './utils' or its corresponding type declarations.
+
+
+==== tests/cases/compiler/index.cjs (2 errors) ====
+    const Blah = require("./blah");
+                         ~~~~~~~~
+!!! error TS2307: Cannot find module './blah' or its corresponding type declarations.
+    const { util1, util2 } = require("./utils");
+                                     ~~~~~~~~~
+!!! error TS2307: Cannot find module './utils' or its corresponding type declarations.
+    
+==== tests/cases/compiler/blah.mjs (0 errors) ====
+    export default class Blah {}
+    
+==== tests/cases/compiler/utils.cjs (0 errors) ====
+    function util1() {}
+    function util2() {}
+    module.exports = { util1, util2 };
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilation_node_cjs_importMissingFileExtension_cjs_mjs.symbols b/tests/baselines/reference/jsFileCompilation_node_cjs_importMissingFileExtension_cjs_mjs.symbols
new file mode 100644
index 0000000000000..06707917e1239
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_node_cjs_importMissingFileExtension_cjs_mjs.symbols
@@ -0,0 +1,10 @@
+=== tests/cases/compiler/index.cjs ===
+const Blah = require("./blah");
+>Blah : Symbol(Blah, Decl(index.cjs, 0, 5))
+>require : Symbol(require)
+
+const { util1, util2 } = require("./utils");
+>util1 : Symbol(util1, Decl(index.cjs, 1, 7))
+>util2 : Symbol(util2, Decl(index.cjs, 1, 14))
+>require : Symbol(require)
+
diff --git a/tests/baselines/reference/jsFileCompilation_node_cjs_importMissingFileExtension_cjs_mjs.types b/tests/baselines/reference/jsFileCompilation_node_cjs_importMissingFileExtension_cjs_mjs.types
new file mode 100644
index 0000000000000..6f23e94ea5b51
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_node_cjs_importMissingFileExtension_cjs_mjs.types
@@ -0,0 +1,14 @@
+=== tests/cases/compiler/index.cjs ===
+const Blah = require("./blah");
+>Blah : any
+>require("./blah") : any
+>require : any
+>"./blah" : "./blah"
+
+const { util1, util2 } = require("./utils");
+>util1 : any
+>util2 : any
+>require("./utils") : any
+>require : any
+>"./utils" : "./utils"
+
diff --git a/tests/baselines/reference/jsFileCompilation_node_js_importMissingFileExtension_cjs_mjs.errors.txt b/tests/baselines/reference/jsFileCompilation_node_js_importMissingFileExtension_cjs_mjs.errors.txt
new file mode 100644
index 0000000000000..1de0b8b097f6f
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_node_js_importMissingFileExtension_cjs_mjs.errors.txt
@@ -0,0 +1,20 @@
+tests/cases/compiler/index.js(1,18): error TS2307: Cannot find module './blah' or its corresponding type declarations.
+tests/cases/compiler/index.js(2,30): error TS2307: Cannot find module './utils' or its corresponding type declarations.
+
+
+==== tests/cases/compiler/blah.mjs (0 errors) ====
+    export default class Blah {}
+    
+==== tests/cases/compiler/utils.cjs (0 errors) ====
+    function util1() {}
+    function util2() {}
+    module.exports = { util1, util2 };
+    
+==== tests/cases/compiler/index.js (2 errors) ====
+    import Blah from "./blah";
+                     ~~~~~~~~
+!!! error TS2307: Cannot find module './blah' or its corresponding type declarations.
+    import { util1, util2 } from "./utils";
+                                 ~~~~~~~~~
+!!! error TS2307: Cannot find module './utils' or its corresponding type declarations.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilation_node_js_importMissingFileExtension_cjs_mjs.symbols b/tests/baselines/reference/jsFileCompilation_node_js_importMissingFileExtension_cjs_mjs.symbols
new file mode 100644
index 0000000000000..9e1ba6c0b4e15
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_node_js_importMissingFileExtension_cjs_mjs.symbols
@@ -0,0 +1,26 @@
+=== tests/cases/compiler/blah.mjs ===
+export default class Blah {}
+>Blah : Symbol(Blah, Decl(blah.mjs, 0, 0))
+
+=== tests/cases/compiler/utils.cjs ===
+function util1() {}
+>util1 : Symbol(util1, Decl(utils.cjs, 0, 0))
+
+function util2() {}
+>util2 : Symbol(util2, Decl(utils.cjs, 0, 19))
+
+module.exports = { util1, util2 };
+>module.exports : Symbol("tests/cases/compiler/utils", Decl(utils.cjs, 0, 0))
+>module : Symbol(export=, Decl(utils.cjs, 1, 19))
+>exports : Symbol(export=, Decl(utils.cjs, 1, 19))
+>util1 : Symbol(util1, Decl(utils.cjs, 2, 18))
+>util2 : Symbol(util2, Decl(utils.cjs, 2, 25))
+
+=== tests/cases/compiler/index.js ===
+import Blah from "./blah";
+>Blah : Symbol(Blah, Decl(index.js, 0, 6))
+
+import { util1, util2 } from "./utils";
+>util1 : Symbol(util1, Decl(index.js, 1, 8))
+>util2 : Symbol(util2, Decl(index.js, 1, 15))
+
diff --git a/tests/baselines/reference/jsFileCompilation_node_js_importMissingFileExtension_cjs_mjs.types b/tests/baselines/reference/jsFileCompilation_node_js_importMissingFileExtension_cjs_mjs.types
new file mode 100644
index 0000000000000..fc323eefacabd
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_node_js_importMissingFileExtension_cjs_mjs.types
@@ -0,0 +1,28 @@
+=== tests/cases/compiler/blah.mjs ===
+export default class Blah {}
+>Blah : Blah
+
+=== tests/cases/compiler/utils.cjs ===
+function util1() {}
+>util1 : () => void
+
+function util2() {}
+>util2 : () => void
+
+module.exports = { util1, util2 };
+>module.exports = { util1, util2 } : { util1: () => void; util2: () => void; }
+>module.exports : { util1: () => void; util2: () => void; }
+>module : { "\"tests/cases/compiler/utils\"": { util1: () => void; util2: () => void; }; }
+>exports : { util1: () => void; util2: () => void; }
+>{ util1, util2 } : { util1: () => void; util2: () => void; }
+>util1 : () => void
+>util2 : () => void
+
+=== tests/cases/compiler/index.js ===
+import Blah from "./blah";
+>Blah : any
+
+import { util1, util2 } from "./utils";
+>util1 : any
+>util2 : any
+
diff --git a/tests/baselines/reference/jsFileCompilation_node_mjs_importMissingFileExtension_cjs_mjs.errors.txt b/tests/baselines/reference/jsFileCompilation_node_mjs_importMissingFileExtension_cjs_mjs.errors.txt
new file mode 100644
index 0000000000000..86f054233ed87
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_node_mjs_importMissingFileExtension_cjs_mjs.errors.txt
@@ -0,0 +1,20 @@
+tests/cases/compiler/index.mjs(1,18): error TS2307: Cannot find module './blah' or its corresponding type declarations.
+tests/cases/compiler/index.mjs(2,30): error TS2307: Cannot find module './utils' or its corresponding type declarations.
+
+
+==== tests/cases/compiler/blah.mjs (0 errors) ====
+    export default class Blah {}
+    
+==== tests/cases/compiler/utils.cjs (0 errors) ====
+    function util1() {}
+    function util2() {}
+    module.exports = { util1, util2 };
+    
+==== tests/cases/compiler/index.mjs (2 errors) ====
+    import Blah from "./blah";
+                     ~~~~~~~~
+!!! error TS2307: Cannot find module './blah' or its corresponding type declarations.
+    import { util1, util2 } from "./utils";
+                                 ~~~~~~~~~
+!!! error TS2307: Cannot find module './utils' or its corresponding type declarations.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilation_node_mjs_importMissingFileExtension_cjs_mjs.symbols b/tests/baselines/reference/jsFileCompilation_node_mjs_importMissingFileExtension_cjs_mjs.symbols
new file mode 100644
index 0000000000000..039028c31beb2
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_node_mjs_importMissingFileExtension_cjs_mjs.symbols
@@ -0,0 +1,26 @@
+=== tests/cases/compiler/blah.mjs ===
+export default class Blah {}
+>Blah : Symbol(Blah, Decl(blah.mjs, 0, 0))
+
+=== tests/cases/compiler/utils.cjs ===
+function util1() {}
+>util1 : Symbol(util1, Decl(utils.cjs, 0, 0))
+
+function util2() {}
+>util2 : Symbol(util2, Decl(utils.cjs, 0, 19))
+
+module.exports = { util1, util2 };
+>module.exports : Symbol("tests/cases/compiler/utils", Decl(utils.cjs, 0, 0))
+>module : Symbol(export=, Decl(utils.cjs, 1, 19))
+>exports : Symbol(export=, Decl(utils.cjs, 1, 19))
+>util1 : Symbol(util1, Decl(utils.cjs, 2, 18))
+>util2 : Symbol(util2, Decl(utils.cjs, 2, 25))
+
+=== tests/cases/compiler/index.mjs ===
+import Blah from "./blah";
+>Blah : Symbol(Blah, Decl(index.mjs, 0, 6))
+
+import { util1, util2 } from "./utils";
+>util1 : Symbol(util1, Decl(index.mjs, 1, 8))
+>util2 : Symbol(util2, Decl(index.mjs, 1, 15))
+
diff --git a/tests/baselines/reference/jsFileCompilation_node_mjs_importMissingFileExtension_cjs_mjs.types b/tests/baselines/reference/jsFileCompilation_node_mjs_importMissingFileExtension_cjs_mjs.types
new file mode 100644
index 0000000000000..3a1ffc5890808
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilation_node_mjs_importMissingFileExtension_cjs_mjs.types
@@ -0,0 +1,28 @@
+=== tests/cases/compiler/blah.mjs ===
+export default class Blah {}
+>Blah : Blah
+
+=== tests/cases/compiler/utils.cjs ===
+function util1() {}
+>util1 : () => void
+
+function util2() {}
+>util2 : () => void
+
+module.exports = { util1, util2 };
+>module.exports = { util1, util2 } : { util1: () => void; util2: () => void; }
+>module.exports : { util1: () => void; util2: () => void; }
+>module : { "\"tests/cases/compiler/utils\"": { util1: () => void; util2: () => void; }; }
+>exports : { util1: () => void; util2: () => void; }
+>{ util1, util2 } : { util1: () => void; util2: () => void; }
+>util1 : () => void
+>util2 : () => void
+
+=== tests/cases/compiler/index.mjs ===
+import Blah from "./blah";
+>Blah : any
+
+import { util1, util2 } from "./utils";
+>util1 : any
+>util2 : any
+
diff --git a/tests/cases/compiler/jsFileCompilation_cjs.ts b/tests/cases/compiler/jsFileCompilation_cjs.ts
new file mode 100644
index 0000000000000..4df902dc9da9a
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilation_cjs.ts
@@ -0,0 +1,17 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+// @filename: a.cjs
+export {}; // error
+import.meta; // error
+
+// @filename: c.cjs
+// this is not in strict mode but class definitions are always in strict mode
+
+class c {
+    a(eval) { //error
+    }
+    method() {
+        var let = 10; // error
+    }
+}
diff --git a/tests/cases/compiler/jsFileCompilation_cjs_importMissingFileExtension_cjs_mjs.ts b/tests/cases/compiler/jsFileCompilation_cjs_importMissingFileExtension_cjs_mjs.ts
new file mode 100644
index 0000000000000..f3ee1a959b3d2
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilation_cjs_importMissingFileExtension_cjs_mjs.ts
@@ -0,0 +1,16 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+// @target: es6
+
+// @filename: blah.mjs
+export default class Blah {}
+
+// @filename: utils.cjs
+function util1() {}
+function util2() {}
+module.exports = { util1, util2 };
+
+// @filename: index.cjs
+const Blah = require("./blah");
+const { util1, util2 } = require("./utils");
diff --git a/tests/cases/compiler/jsFileCompilation_js_importMissingFileExtension_cjs_mjs.ts b/tests/cases/compiler/jsFileCompilation_js_importMissingFileExtension_cjs_mjs.ts
new file mode 100644
index 0000000000000..f9e0376be64cc
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilation_js_importMissingFileExtension_cjs_mjs.ts
@@ -0,0 +1,16 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+// @target: es6
+
+// @filename: blah.mjs
+export default class Blah {}
+
+// @filename: utils.cjs
+function util1() {}
+function util2() {}
+module.exports = { util1, util2 };
+
+// @filename: index.js
+import Blah from "./blah";
+import { util1, util2 } from "./utils";
diff --git a/tests/cases/compiler/jsFileCompilation_mjs.ts b/tests/cases/compiler/jsFileCompilation_mjs.ts
new file mode 100644
index 0000000000000..a01ac999a3f08
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilation_mjs.ts
@@ -0,0 +1,40 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+// @target: es6
+// @filename: a.mjs
+// `.mjs` files are automatically external modules, and thus in strict mode
+
+var a = {
+    a: "hello", // error
+    b: 10,
+    a: 10 // error
+};
+var let = 10; // error
+delete a; // error
+try {
+} catch (eval) { // error
+}
+function arguments() { // error
+}
+
+with (a) {
+    b = 10;
+}
+
+// @filename: b.mjs
+class c {
+    a(eval) { //error
+    }
+    method() {
+        var let = 10; // error
+    }
+}
+
+// @filename: c.mjs
+var let = 10;
+var eval = function () {
+};
+
+//@filename: d.mjs
+var x = 009; // error
diff --git a/tests/cases/compiler/jsFileCompilation_mjs_importMissingFileExtension_cjs_mjs.ts b/tests/cases/compiler/jsFileCompilation_mjs_importMissingFileExtension_cjs_mjs.ts
new file mode 100644
index 0000000000000..eef7c75a9fa69
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilation_mjs_importMissingFileExtension_cjs_mjs.ts
@@ -0,0 +1,16 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+// @target: es6
+
+// @filename: blah.mjs
+export default class Blah {}
+
+// @filename: utils.cjs
+function util1() {}
+function util2() {}
+module.exports = { util1, util2 };
+
+// @filename: index.mjs
+import Blah from "./blah";
+import { util1, util2 } from "./utils";
diff --git a/tests/cases/compiler/jsFileCompilation_node_cjs_importMissingFileExtension_cjs_mjs.ts b/tests/cases/compiler/jsFileCompilation_node_cjs_importMissingFileExtension_cjs_mjs.ts
new file mode 100644
index 0000000000000..0dee2a24e1b66
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilation_node_cjs_importMissingFileExtension_cjs_mjs.ts
@@ -0,0 +1,17 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+// @target: es6
+// @moduleResolution: node
+
+// @filename: blah.mjs
+export default class Blah {}
+
+// @filename: utils.cjs
+function util1() {}
+function util2() {}
+module.exports = { util1, util2 };
+
+// @filename: index.cjs
+const Blah = require("./blah");
+const { util1, util2 } = require("./utils");
diff --git a/tests/cases/compiler/jsFileCompilation_node_js_importMissingFileExtension_cjs_mjs.ts b/tests/cases/compiler/jsFileCompilation_node_js_importMissingFileExtension_cjs_mjs.ts
new file mode 100644
index 0000000000000..e10bdfffe4904
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilation_node_js_importMissingFileExtension_cjs_mjs.ts
@@ -0,0 +1,17 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+// @target: es6
+// @moduleResolution: node
+
+// @filename: blah.mjs
+export default class Blah {}
+
+// @filename: utils.cjs
+function util1() {}
+function util2() {}
+module.exports = { util1, util2 };
+
+// @filename: index.js
+import Blah from "./blah";
+import { util1, util2 } from "./utils";
diff --git a/tests/cases/compiler/jsFileCompilation_node_mjs_importMissingFileExtension_cjs_mjs.ts b/tests/cases/compiler/jsFileCompilation_node_mjs_importMissingFileExtension_cjs_mjs.ts
new file mode 100644
index 0000000000000..c07b23caaf0f9
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilation_node_mjs_importMissingFileExtension_cjs_mjs.ts
@@ -0,0 +1,17 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+// @target: es6
+// @moduleResolution: node
+
+// @filename: blah.mjs
+export default class Blah {}
+
+// @filename: utils.cjs
+function util1() {}
+function util2() {}
+module.exports = { util1, util2 };
+
+// @filename: index.mjs
+import Blah from "./blah";
+import { util1, util2 } from "./utils";
diff --git a/tests/cases/fourslash/importNameCodeFix_cjs.ts b/tests/cases/fourslash/importNameCodeFix_cjs.ts
new file mode 100644
index 0000000000000..7c82ba35a25f1
--- /dev/null
+++ b/tests/cases/fourslash/importNameCodeFix_cjs.ts
@@ -0,0 +1,36 @@
+/// <reference path="fourslash.ts" />
+
+// @allowJs: true
+// @checkJs: true
+
+// @Filename: foo.cjs
+////module.exports = function foo() {}
+
+// @Filename: utils.cjs
+////function util1() {}
+////function util2() {}
+////module.exports = { util1, util2 };
+
+// @Filename: blah.js
+////export default class Blah {}
+
+// @Filename: index.cjs
+////foo();
+////util1();
+////util2();
+////new Blah;
+
+goTo.file("index.cjs");
+verify.codeFixAll({
+  fixId: "fixMissingImport",
+  fixAllDescription: "Add all missing imports",
+  newFileContent:
+`const { default: Blah } = require("./blah");
+const foo = require("./foo.cjs");
+const { util1, util2 } = require("./utils.cjs");
+
+foo();
+util1();
+util2();
+new Blah;`
+});
diff --git a/tests/cases/fourslash/importNameCodeFix_mjs.ts b/tests/cases/fourslash/importNameCodeFix_mjs.ts
new file mode 100644
index 0000000000000..85437e9059559
--- /dev/null
+++ b/tests/cases/fourslash/importNameCodeFix_mjs.ts
@@ -0,0 +1,36 @@
+/// <reference path="fourslash.ts" />
+
+// @allowJs: true
+// @checkJs: true
+
+// @Filename: foo.js
+////module.exports = function foo() {}
+
+// @Filename: utils.cjs
+////function util1() {}
+////function util2() {}
+////module.exports = { util1, util2 };
+
+// @Filename: blah.mjs
+////export default class Blah {}
+
+// @Filename: index.mjs
+////foo();
+////util1();
+////util2();
+////new Blah;
+
+goTo.file("index.mjs");
+verify.codeFixAll({
+  fixId: "fixMissingImport",
+  fixAllDescription: "Add all missing imports",
+  newFileContent:
+`import Blah from "./blah.mjs";
+import foo from "./foo.js";
+import { util1, util2 } from "./utils.cjs";
+
+foo();
+util1();
+util2();
+new Blah;`
+});
diff --git a/tests/cases/fourslash/importNameCodeFix_require_cjs_and_mjs.ts b/tests/cases/fourslash/importNameCodeFix_require_cjs_and_mjs.ts
new file mode 100644
index 0000000000000..dd8f4cc903e0b
--- /dev/null
+++ b/tests/cases/fourslash/importNameCodeFix_require_cjs_and_mjs.ts
@@ -0,0 +1,36 @@
+/// <reference path="fourslash.ts" />
+
+// @allowJs: true
+// @checkJs: true
+
+// @Filename: foo.js
+////module.exports = function foo() {}
+
+// @Filename: utils.cjs
+////function util1() {}
+////function util2() {}
+////module.exports = { util1, util2 };
+
+// @Filename: blah.mjs
+////export default class Blah {}
+
+// @Filename: index.js
+////foo();
+////util1();
+////util2();
+////new Blah;
+
+goTo.file("index.js");
+verify.codeFixAll({
+  fixId: "fixMissingImport",
+  fixAllDescription: "Add all missing imports",
+  newFileContent:
+`const { default: Blah } = require("./blah.mjs");
+const foo = require("./foo");
+const { util1, util2 } = require("./utils.cjs");
+
+foo();
+util1();
+util2();
+new Blah;`
+});