perf: improve the internal config set function (#5872)

The function is now almost twice as fast and doesn't create any temprary
objects in memory.

Author: watson

packages/datadog-core/src/utils/src/set.js

@@ -1,16 +1,14 @@
 'use strict'
 
 module.exports = function set (object, path, value) {
-  const pathArr = path.split('.')
-  let property = object
-  let i
-  for (i = 0; i < pathArr.length - 1; i++) {
-    const n = pathArr[i]
-    if (property.hasOwnProperty(n)) {
-      property = property[n]
-    } else {
-      property[n] = property = {}
+  let index = -1
+  while (true) {
+    const nextIndex = path.indexOf('.', index + 1)
+    if (nextIndex === -1) {
+      object[path.slice(index + 1)] = value
+      return
     }
+    object = object[path.slice(index + 1, nextIndex)] ??= {}
+    index = nextIndex
   }
-  property[pathArr[i]] = value
 }

packages/datadog-core/test/utils/src/set.spec.js

@@ -9,7 +9,9 @@ describe('set', () => {
   const obj = {}
 
   it('should set value at path', () => {
-    set(obj, 'a.b', 'c')
-    expect(obj.a.b).to.be.equal('c')
+    set(obj, 'a', 1)
+    set(obj, 'b.c', 2)
+    set(obj, 'b.d.e', 3)
+    expect(obj).to.deep.equal({ a: 1, b: { c: 2, d: { e: 3 } } })
   })
 })