Add Polyfills for IE11.

.gitignore

@@ -42,3 +42,5 @@ $virtualenv.tar.gz
 *.log
 *.pot
 bin
+
+.vscode/

package.json

@@ -50,12 +50,14 @@
     }
   },
   "dependencies": {
-    "react": "^15.4.2",
-    "react-dom": "^15.4.2",
+    "draft-js": "^0.10.0",
+    "draftail": "^0.6.0",
+    "promise": "^8.0.0",
     "prop-types": "^15.5.8",
+    "react": "^15.4.2",
     "react-autosuggest": "^3.7.4",
-    "draft-js": "^0.10.0",
-    "draftail": "^0.6.0"
+    "react-dom": "^15.4.2",
+    "whatwg-fetch": "^2.0.3"
   },
   "devDependencies": {
     "babel-core": "^6.22.1",
@@ -82,5 +84,5 @@
     "start": "webpack --config wagtailmodelchoosers/client/webpack.config.dev.js --watch",
     "dist": "webpack --config wagtailmodelchoosers/client/webpack.config.prod.js",
     "lint": "eslint wagtailmodelchoosers/client"
-}
+  }
 }

wagtailmodelchoosers/client/polyfills.js

@@ -0,0 +1,66 @@
+/**
+ * This file is automatically included in the JS bundle.
+ * Don't import it manually.
+ */
+
+if (typeof Promise === 'undefined') {
+    // Rejection tracking prevents a common issue where React gets into an
+    // inconsistent state due to an error, but it gets swallowed by a Promise,
+    // and the user has no idea what causes React's erratic future behavior.
+    /* eslint-disable global-require */
+  require('promise/lib/rejection-tracking').enable();
+  window.Promise = require('promise/lib/es6-extensions.js');
+    /* eslint-enable */
+}
+
+// fetch() polyfill for making API calls.
+// Uncomment this line to use fetch in your code.
+// It is left out by default, because the polyfill is big.
+require('whatwg-fetch');
+
+/* eslint-disable */
+// https://tc39.github.io/ecma262/#sec-array.prototype.find
+if (!Array.prototype.find) {
+    Object.defineProperty(Array.prototype, 'find', {
+        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 kValue.
+            var kValue = o[k];
+            if (predicate.call(thisArg, kValue, k, o)) {
+            return kValue;
+            }
+            // e. Increase k by 1.
+            k++;
+        }
+
+        // 7. Return undefined.
+        return undefined;
+        }
+    });
+}
+/* eslint-enable */

wagtailmodelchoosers/client/webpack.config.dev.js

@@ -7,6 +7,7 @@ const outputPath = path.join(__dirname, '..', 'static', 'wagtailmodelchoosers');
 module.exports = {
   entry: {
     wagtailmodelchoosers: './wagtailmodelchoosers/client/wagtailmodelchoosers.js',
+    polyfills: './wagtailmodelchoosers/client/polyfills.js',
   },
   output: {
     path: outputPath,

wagtailmodelchoosers/wagtail_hooks.py

@@ -1,6 +1,6 @@
 from django.conf.urls import url
 from django.contrib.staticfiles.templatetags.staticfiles import static
-from django.utils.html import format_html
+from django.utils.html import format_html, format_html_join
 
 from wagtail.wagtailcore import hooks
 
@@ -17,10 +17,16 @@ def wagtailmodelchoosers_admin_css():
 
 @hooks.register('insert_editor_js')
 def wagtailmodelchoosers_admin_js():
-    return format_html(
+    js_files = (
+        'wagtailmodelchoosers/wagtailmodelchoosers.js',
+        'wagtailmodelchoosers/polyfills.js',
+    )
+    js_includes = format_html_join(
+        '\n',
         '<script src="{}"></script>',
-        static('wagtailmodelchoosers/wagtailmodelchoosers.js')
+        ((static(filename),) for filename in js_files)
     )
+    return js_includes
 
 
 @hooks.register('register_admin_urls')