Use core js for polyfills

package.json

@@ -40,7 +40,6 @@
     "babel-preset-stage-2": "^6.24.1",
     "chai": "^4.1.0",
     "concurrently": "^3.1.0",
-    "core-js": "^2.4.1",
     "csso": "^1.8.2",
     "custom-event-autopolyfill": "^0.1.3",
     "es6-promise": "^3.2.1",
@@ -71,7 +70,8 @@
     "classnames": "^2.2.5",
     "fuse.js": "^3.1.0",
     "opn": "^5.1.0",
-    "redux": "^3.3.1"
+    "redux": "^3.3.1",
+    "core-js": "^2.5.6"
   },
   "npmName": "choices.js",
   "npmFileMap": [

src/scripts/src/lib/polyfills.js

@@ -1,125 +1,13 @@
-/* eslint-disable */
-(function () {
-  // Production steps of ECMA-262, Edition 6, 22.1.2.1
-  // Reference: https://people.mozilla.org/~jorendorff/es6-draft.html#sec-array.from
-  if (!Array.from) {
-    Array.from = (function() {
-      let toStr = Object.prototype.toString;
+import 'core-js/fn/array/from';
+import 'core-js/fn/array/find';
 
-      let isCallable = function(fn) {
-        return typeof fn === 'function' || toStr.call(fn) === '[object Function]';
-      };
-
-      let toInteger = function(value) {
-        let number = Number(value);
-        if (isNaN(number)) {
-          return 0;
-        }
-        if (number === 0 || !isFinite(number)) {
-          return number;
-        }
-        return (number > 0 ? 1 : -1) * Math.floor(Math.abs(number));
-      };
-
-      let maxSafeInteger = Math.pow(2, 53) - 1;
-
-      let toLength = function(value) {
-        let len = toInteger(value);
-        return Math.min(Math.max(len, 0), maxSafeInteger);
-      };
-
-      // The length property of the from method is 1.
-      return function from(arrayLike /* , mapFn, thisArg */) {
-        // 1. Let C be the this value.
-        let C = this;
-
-        // 2. Let items be ToObject(arrayLike).
-        let items = Object(arrayLike);
-
-        // 3. ReturnIfAbrupt(items).
-        if (arrayLike == null) {
-          throw new TypeError('Array.from requires an array-like object - not null or undefined');
-        }
-
-        // 4. If mapfn is undefined, then let mapping be false.
-        let mapFn = arguments.length > 1 ? arguments[1] : void undefined;
-        let T;
-        if (typeof mapFn !== 'undefined') {
-          // 5. else
-          // 5. a If IsCallable(mapfn) is false, throw a TypeError exception.
-          if (!isCallable(mapFn)) {
-            throw new TypeError('Array.from: when provided, the second argument must be a function');
-          }
-
-          // 5. b. If thisArg was supplied, let T be thisArg; else let T be undefined.
-          if (arguments.length > 2) {
-            T = arguments[2];
-          }
-        }
-
-        // 10. Let lenValue be Get(items, "length").
-        // 11. Let len be ToLength(lenValue).
-        let len = toLength(items.length);
-
-        // 13. If IsConstructor(C) is true, then
-        // 13. a. Let A be the result of calling the [[Construct]] internal method of C with an argument list containing the single item len.
-        // 14. a. Else, Let A be ArrayCreate(len).
-        let A = isCallable(C) ? Object(new C(len)) : new Array(len);
-
-        // 16. Let k be 0.
-        let k = 0;
-        // 17. Repeat, while k < len… (also steps a - h)
-        let kValue;
-        while (k < len) {
-          kValue = items[k];
-          if (mapFn) {
-            A[k] = typeof T === 'undefined' ? mapFn(kValue, k) : mapFn.call(T, kValue, k);
-          } else {
-            A[k] = kValue;
-          }
-          k += 1;
-        }
-        // 18. Let putStatus be Put(A, "length", len, true).
-        A.length = len;
-        // 20. Return A.
-        return A;
-      };
-    }());
+(function CustomEventPolyfill() {
+  if (typeof window.CustomEvent === 'function') {
+    return false;
   }
 
-  // Reference: https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Array/find
-  if (!Array.prototype.find) {
-    Array.prototype.find = function(predicate) {
-      'use strict';
-
-      if (this == null) {
-        throw new TypeError('Array.prototype.find called on null or undefined');
-      }
-      if (typeof predicate !== 'function') {
-        throw new TypeError('predicate must be a function');
-      }
-      let list = Object(this);
-      let length = list.length >>> 0;
-      let thisArg = arguments[1];
-      let value;
-
-      for (let i = 0; i < length; i++) {
-        value = list[i];
-        if (predicate.call(thisArg, value, i, list)) {
-          return value;
-        }
-      }
-      return undefined;
-    };
-  }
-
-  function CustomEvent (event, params) {
-    params = params || {
-      bubbles: false,
-      cancelable: false,
-      detail: undefined,
-    };
-    let evt = document.createEvent('CustomEvent');
+  function CustomEvent (event, params = { bubbles: false, cancelable: false, detail: undefined }) {
+    const evt = document.createEvent('CustomEvent');
     evt.initCustomEvent(event, params.bubbles, params.cancelable, params.detail);
     return evt;
   }