Shim refactor (#550)

* Refactor to organize shims by Object

* [AUTOMATED]: Prettier Code Styling

* [AUTOMATED]: License Headers

Author: jshcrowthe

packages/polyfill/index.ts

@@ -15,5 +15,5 @@
  */
 
 import './src/polyfills/promise';
-import './src/shims/find';
-import './src/shims/findIndex';
+import './src/shims/Array';
+import './src/shims/String';

packages/polyfill/src/shims/findIndex.ts renamed to packages/polyfill/src/shims/Array.ts

@@ -14,6 +14,55 @@
  * limitations under the License.
  */
 
+/**
+ * This is the Array.prototype.find polyfill from MDN
+ * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find
+ * 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;
+    }
+  });
+}
+
 /**
  * This is the Array.prototype.findIndex polyfill from MDN
  * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/findIndex

packages/polyfill/src/shims/String.ts

@@ -0,0 +1,25 @@
+/**
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * This is the String.prototype.startsWith polyfill from MDN
+ * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/startsWith
+ */
+if (!String.prototype.startsWith) {
+  String.prototype.startsWith = function(search, pos) {
+    return this.substr(!pos || pos < 0 ? 0 : +pos, search.length) === search;
+  };
+}