adds polyfill for Object.assign, fix for IE11

app/assets/javascripts/application.js.erb

@@ -13,6 +13,7 @@
 //= require jquery
 //= require jquery_ujs
 //= require bootstrap
+//= require polyfill
 //= require jquery-ui/ui/jquery.ui.core
 //= require jquery-ui/ui/jquery.ui.widget
 //= require jquery-ui/ui/jquery.ui.mouse

lib/assets/javascripts/polyfill.js

@@ -0,0 +1,29 @@
+if (typeof Object.assign != 'function') {
+  // Must be writable: true, enumerable: false, configurable: true
+  Object.defineProperty(Object, "assign", {
+    value: function assign(target, varArgs) { // .length of function is 2
+      'use strict';
+      if (target == null) { // TypeError if undefined or null
+        throw new TypeError('Cannot convert undefined or null to object');
+      }
+
+      var to = Object(target);
+
+      for (var index = 1; index < arguments.length; index++) {
+        var nextSource = arguments[index];
+
+        if (nextSource != null) { // Skip over if undefined or null
+          for (var nextKey in nextSource) {
+            // Avoid bugs when hasOwnProperty is shadowed
+            if (Object.prototype.hasOwnProperty.call(nextSource, nextKey)) {
+              to[nextKey] = nextSource[nextKey];
+            }
+          }
+        }
+      }
+      return to;
+    },
+    writable: true,
+    configurable: true
+  });
+}