Array.findIndex() poly for IE11

demo/column.html

@@ -11,6 +11,7 @@
 
   <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
   <script src="../dist/jquery-ui.min.js"></script>
+  <script src="../src/gridstack-poly.js"></script>
   <script src="../src/gridstack.js"></script>
   <script src="../src/gridstack.jQueryUI.js"></script>
 </head>
@@ -36,9 +37,9 @@ <h1>setColumn() grid demo</h1>
       $grid.gridstack({float: true});
       grid = $grid.data('gridstack');
 
-      $grid.on('added', (e, items) => log(' added ', items));
-      $grid.on('removed', (e, items) => log(' removed ', items));
-      $grid.on('change', (e, items) => log(' change ', items));
+      $grid.on('added', function(e, items) {log(' added ', items)});
+      $grid.on('removed', function(e, items) {log(' removed ', items)});
+      $grid.on('change', function(e, items) {log(' change ', items)});
       function log(type, items) {
         if (!items) { return; }
         var str = '';
@@ -63,7 +64,7 @@ <h1>setColumn() grid demo</h1>
       };
       grid.commit();
 
-      $('#add-widget').click(() => {
+      $('#add-widget').click(function() {
         var node = items.pop() || {
           x: Math.round(12 * Math.random()),
           y: Math.round(5 * Math.random()),
@@ -73,15 +74,15 @@ <h1>setColumn() grid demo</h1>
         grid.addWidget($('<div><div class="grid-stack-item-content">' + count++ + '</div></div>'), node);
       });
 
-      $('#1column').click(() => { grid.setColumn(1); });
-      $('#2column').click(() => { grid.setColumn(2); });
-      $('#3column').click(() => { grid.setColumn(3); });
-      $('#4column').click(() => { grid.setColumn(4); });
-      $('#6column').click(() => { grid.setColumn(6); });
-      $('#6column').click(() => { grid.setColumn(6); });
-      $('#8column').click(() => { grid.setColumn(8); });
-      $('#10column').click(() => { grid.setColumn(10); });
-      $('#12column').click(() => { grid.setColumn(12); });
+      $('#1column').click(function() { grid.setColumn(1); });
+      $('#2column').click(function() { grid.setColumn(2); });
+      $('#3column').click(function() { grid.setColumn(3); });
+      $('#4column').click(function() { grid.setColumn(4); });
+      $('#6column').click(function() { grid.setColumn(6); });
+      $('#6column').click(function() { grid.setColumn(6); });
+      $('#8column').click(function() { grid.setColumn(8); });
+      $('#10column').click(function() { grid.setColumn(10); });
+      $('#12column').click(function() { grid.setColumn(12); });
     });
   </script>
 </body>

src/gridstack-poly.js

@@ -10,7 +10,7 @@ Number.isNaN = Number.isNaN || function isNaN(input) {
   return typeof input === 'number' && input !== input;
 }
 
-// https://tc39.github.io/ecma262/#sec-array.prototype.find
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find
 if (!Array.prototype.find) {
   Object.defineProperty(Array.prototype, 'find', {
     value: function (predicate) {
@@ -55,4 +55,51 @@ if (!Array.prototype.find) {
     configurable: true,
     writable: true
   });
+}
+
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/findIndex
+if (!Array.prototype.findIndex) {
+  Object.defineProperty(Array.prototype, 'findIndex', {
+    value: function(predicate) {
+      // 1. Let O be ? ToObject(this value).
+      if (this == null) {
+        throw new TypeError('"this" is null or not defined');
+      }
+
+      var o = Object(this);
+
+      // 2. Let len be ? ToLength(? Get(O, "length")).
+      var len = o.length >>> 0;
+
+      // 3. If IsCallable(predicate) is false, throw a TypeError exception.
+      if (typeof predicate !== 'function') {
+        throw new TypeError('predicate must be a function');
+      }
+
+      // 4. If thisArg was supplied, let T be thisArg; else let T be undefined.
+      var thisArg = arguments[1];
+
+      // 5. Let k be 0.
+      var k = 0;
+
+      // 6. Repeat, while k < len
+      while (k < len) {
+        // a. Let Pk be ! ToString(k).
+        // b. Let kValue be ? Get(O, Pk).
+        // c. Let testResult be ToBoolean(? Call(predicate, T, « kValue, k, O »)).
+        // d. If testResult is true, return k.
+        var kValue = o[k];
+        if (predicate.call(thisArg, kValue, k, o)) {
+          return k;
+        }
+        // e. Increase k by 1.
+        k++;
+      }
+
+      // 7. Return -1.
+      return -1;
+    },
+    configurable: true,
+    writable: true
+  });
 }

src/jquery-ui.js

@@ -399,7 +399,7 @@ $.Widget.prototype = {
 
     if ( typeof key === "string" ) {
 
-      // Handle nested keys, e.g., "foo.bar" => { foo: { bar: ___ } }
+      // Handle nested keys, e.g., "foo.bar" = { foo: { bar: ___ } }
       options = {};
       parts = key.split( "." );
       key = parts.shift();