Fix enumerable array polyfill

src/utils/polyfill.js

@@ -1,38 +1,63 @@
-/**
- * Array.prototype.find()
- * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find
- */
-(function() {
-  function polyfill(fnName) {
-    if (!Array.prototype[fnName]) {
-      Array.prototype[fnName] = function(predicate /*, thisArg */ ) {
-        var i, len, test, thisArg = arguments[1];
-
-        if (typeof predicate !== "function") {
-          throw new TypeError();
+(function () {
+  /**
+   * 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) {
+        'use strict';
+        if (this == null) {
+          throw new TypeError('Array.prototype.find called on null or undefined');
         }
-
-        test = !thisArg ? predicate : function() {
-          return predicate.apply(thisArg, arguments);
-        };
-
-        for (i = 0, len = this.length; i < len; i++) {
-          if (test(this[i], i, this) === true) {
-            return fnName === "find" ? this[i] : i;
-          }
+        if (typeof predicate !== 'function') {
+          throw new TypeError('predicate must be a function');
         }
+        var list = Object(this);
+        var length = list.length >>> 0;
+        var thisArg = arguments[1];
+        var value;
 
-        if (fnName !== "find") {
-          return -1;
+        for (var i = 0; i < length; i++) {
+          value = list[i];
+          if (predicate.call(thisArg, value, i, list)) {
+            return value;
+          }
         }
-      };
-    }
+        return undefined;
+      }
+    });
   }
+  /**
+   * Array.prototype.findIndex()
+   * 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) {
+        'use strict';
+        if (this == null) {
+          throw new TypeError('Array.prototype.findIndex called on null or undefined');
+        }
+        if (typeof predicate !== 'function') {
+          throw new TypeError('predicate must be a function');
+        }
+        var list = Object(this);
+        var length = list.length >>> 0;
+        var thisArg = arguments[1];
+        var value;
 
-  for (var i in {
-      find: 1,
-      findIndex: 1
-    }) {
-    polyfill(i);
+        for (var i = 0; i < length; i++) {
+          value = list[i];
+          if (predicate.call(thisArg, value, i, list)) {
+            return i;
+          }
+        }
+        return -1;
+      },
+      enumerable: false,
+      configurable: false,
+      writable: false
+    });
   }
 }());