diff --git a/js/TimeExplorer.js b/js/TimeExplorer.js
index c01f558..c1da414 100644
--- a/js/TimeExplorer.js
+++ b/js/TimeExplorer.js
@@ -515,15 +515,14 @@ class TimeExplorer {
    * @param {string} sheet_id - ID of Google spreadsheet containing data
    */
   get_sheet_data(sheet_id) {
-    var self = this;
-    var dfd = $.Deferred();
-    var request_url = `https://sheets.googleapis.com/v4/spreadsheets/${sheet_id}/values/A:ZZZ?key=${this.api_key}`;
+    let self = this;
+    let dfd = $.Deferred();
+    const request_url = `https://sheets.googleapis.com/v4/spreadsheets/${sheet_id}/values/A:ZZZ?key=${this.api_key}`;
     $.getJSON(request_url).done(function(data) {
-      var columns = data.values[0];
-      for (var i = 1; i < data.values.length; i++) {
-        var values = zip_arrays(columns, data.values[i]);
-        self.sheet_data.push(values);
-      };
+      let columns = data.values[0];
+      self.sheet_data = data.values.slice(1).map( (item)=> {
+        return zip_arrays(columns,item);
+      });
       dfd.resolve();
     });
     return dfd.promise();
diff --git a/js/TimeExplorerSpec.js b/js/TimeExplorerSpec.js
index 66a25ab..4cc1ea9 100644
--- a/js/TimeExplorerSpec.js
+++ b/js/TimeExplorerSpec.js
@@ -107,6 +107,18 @@ describe('Testing the TimeExplorer class', () => {
     expect(tags).toEqual('Tags');
   })
 
+  it('TimeExplorer.create_timeline() should create a timeline', ()=> {
+    explorer = new_explorer()
+    const timeline = explorer.create_timeline(explorer.options);
+    expect(Object.keys(timeline)).toContain('itemsData');
+  })
+
+  it('TimeExplorer.get_sheet_data() should return a promise', ()=> {
+    explorer = new_explorer()
+    const sheetData = explorer.get_sheet_data(api_key);
+    expect(Object.keys(sheetData)).toContain("promise");
+  })
+
   it('TimeExplorer.set_options() should extend options', ()=> {
     explorer = new_explorer()
     const r = explorer.set_options(["Joe"])