Advance ECMAScript 2017 additions to es2017.js script

inexorabletash · Nov 5, 2017 · 84cb3b3 · 84cb3b3
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diff --git a/README.md b/README.md
@@ -33,12 +33,12 @@ Since I generally use several in my hobby projects, bundled/minified versions ar
 
 * [web.js](web.js) (minified: [web.min.js](web.min.js)) includes the most common Web polyfills - it assumes ES2015 support
   * Includes: [html.js](html.js) [dom.js](dom.js) [xhr.js](xhr.js) [cssom.js](cssom.js) [url.js](url.js) [fetch.js](fetch.js)
-* [polyfill.js](polyfill.js) (minified: [polyfill.min.js](polyfill.min.js)) has everything in [web.js](web.js) plus [es5.js](es5.js) and [es6.js](es6.js) and [es2016.js](es2016.js)
+* [polyfill.js](polyfill.js) (minified: [polyfill.min.js](polyfill.min.js)) has everything in [web.js](web.js) plus [es5.js](es5.js) and [es6.js](es6.js) and [es2016.js](es2016.js) and [es2017.js](es2017.js)
 
 Minification is done via https://github.com/mishoo/UglifyJS2
 
 > Some of the files use `console.assert()` calls to catch bugs during development. These are
-> automatically removed from the included minified versions. If you use your own minifying 
+> automatically removed from the included minified versions. If you use your own minifying
 > processor it may cause to assertions to appear when unnecessary function names are stripped.
 > You can safely remove these lines as part of a build step (e.g. using `grep -V`), or use a
 > minifier that does this automatically. For [UglifyJS2](https://github.com/mishoo/UglifyJS2)
@@ -52,7 +52,9 @@ ECMAScript / JavaScript Polyfills
 
 [ECMAScript 2015](es6.md) - Previous standard, supported by browsers circa 2016.
 
-[ECMAScript 2016](es2016.md) - Most recent standard. Not fully supported by modern browsers yet.
+[ECMAScript 2016](es2016.md) - Previous standard, supported by browsers circa 2017.
+
+[ECMAScript 2017](es2017.md) - Most recent standard. Implementation in progress or complete in latest browsers.
 
 [ECMAScript proposed](experimental/es-proposed.md) - Proposals for future editions of the standard. Here there be dragons.
 

diff --git a/es2017.js b/es2017.js
@@ -0,0 +1,208 @@
+//----------------------------------------------------------------------
+//
+// ECMAScript 2017 Polyfills
+//
+//----------------------------------------------------------------------
+
+(function (global) {
+  'use strict';
+  var undefined = (void 0); // Paranoia
+
+  // Helpers
+
+  function isSymbol(s) {
+    return (typeof s === 'symbol') || ('Symbol' in global && s instanceof global.Symbol);
+  }
+
+  function define(o, p, v, override) {
+    if (p in o && !override)
+      return;
+
+    if (typeof v === 'function') {
+      // Sanity check that functions are appropriately named (where possible)
+      console.assert(isSymbol(p) || !('name' in v) || v.name === p || v.name === p + '_', 'Expected function name "' + p.toString() + '", was "' + v.name + '"');
+      Object.defineProperty(o, p, {
+        value: v,
+        configurable: true,
+        enumerable: false,
+        writable: true
+      });
+    } else {
+      Object.defineProperty(o, p, {
+        value: v,
+        configurable: false,
+        enumerable: false,
+        writable: false
+      });
+    }
+  }
+
+  // Snapshot intrinsic functions
+  var $isNaN = global.isNaN;
+
+  var abs = Math.abs,
+      floor = Math.floor,
+      min = Math.min;
+
+  //----------------------------------------
+  // 7 Abstract Operations
+  //----------------------------------------
+
+  // 7.1.4
+  function ToInteger(n) {
+    n = Number(n);
+    if ($isNaN(n)) return 0;
+    if (n === 0 || n === Infinity || n === -Infinity) return n;
+    return ((n < 0) ? -1 : 1) * floor(abs(n));
+  }
+
+  // 7.1.13 ToObject
+  function ToObject(v) {
+    if (v === null || v === undefined) throw TypeError();
+    return Object(v);
+  }
+
+  // 7.1.15 ToLength ( argument )
+  function ToLength(v) {
+    var len = ToInteger(v);
+    if (len <= 0) {
+      return 0;
+    }
+    return min(len, 0x20000000000000 - 1); // 2^53-1
+  }
+
+  //----------------------------------------
+  // 7.3 Operations on Objects
+  //----------------------------------------
+
+  // 7.3.4
+  function CreateDataProperty(O, P, V) {
+    Object.defineProperty(O, P, {
+      value: V,
+      writable: true,
+      enumerable: true,
+      configurable: true
+    });
+  }
+
+  // 7.3.21
+  function EnumerableOwnProperties(o, kind) {
+    var ownKeys = Object.keys(o);
+    var properties = [];
+    ownKeys.forEach(function(key) {
+      var desc = Object.getOwnPropertyDescriptor(o, key);
+      if (desc && desc.enumerable) {
+        if (kind === 'key') properties.push(key);
+        else {
+          var value = o[key];
+          if (kind === 'value') properties.push(value);
+          else properties.push([key, value]);
+        }
+      }
+    });
+    return properties;
+  }
+
+
+  //----------------------------------------------------------------------
+  // 19 Fundamental Objects
+  //----------------------------------------------------------------------
+
+  // 19.1 Object Objects
+  // 19.1.2 Properties of the Object Constructor
+
+  // 19.1.2.5 Object.entries
+  define(
+    Object, 'entries',
+    function entries(o) {
+      var obj = ToObject(o);
+      return EnumerableOwnProperties(obj, 'key+value');
+    });
+
+  // 19.1.2.8 Object.getOwnPropertyDescriptors ( O )
+  define(
+    Object, 'getOwnPropertyDescriptors',
+    function getOwnPropertyDescriptors(o) {
+      var obj = ToObject(o);
+      // ReturnIfAbrupt(obj)
+      var keys = Object.getOwnPropertyNames(obj);
+      // ReturnIfAbrupt(keys)
+      var descriptors = {};
+      for (var i = 0; i < keys.length; ++i) {
+        var nextKey = keys[i];
+        var descriptor = Object.getOwnPropertyDescriptor(obj, nextKey);
+        // ReturnIfAbrupt(desc)
+        // ReturnIfAbrupt(descriptor)
+        CreateDataProperty(descriptors, nextKey, descriptor);
+      }
+      return descriptors;
+    });
+
+  // 19.1.2.21 Object.values
+  define(
+    Object, 'values',
+    function values(o) {
+      var obj = ToObject(o);
+      return EnumerableOwnProperties(obj, 'value');
+    });
+
+
+
+  //----------------------------------------------------------------------
+  // 21 Text Processing
+  //----------------------------------------------------------------------
+
+  // 21.1 String Objects
+  // 21.1.3 Properties of the String Prototype Object
+
+  // 21.1.3.13 String.prototype.padEnd( maxLength [ , fillString ] )
+  define(
+    String.prototype, 'padEnd',
+    function padEnd(maxLength) {
+      var fillString = arguments[1];
+
+      var o = this;
+      // ReturnIfAbrupt(o)
+      var s = String(this);
+      // ReturnIfAbrupt(s)
+      var stringLength = s.length;
+      if (fillString === undefined) var fillStr = '';
+      else fillStr = String(fillString);
+      // ReturnIfAbrupt(fillStr)
+      if (fillStr === '') fillStr = ' ';
+      var intMaxLength = ToLength(maxLength);
+      // ReturnIfAbrupt(intMaxLength)
+      if (intMaxLength <= stringLength) return s;
+      var fillLen = intMaxLength - stringLength;
+      var stringFiller = '';
+      while (stringFiller.length < fillLen)
+        stringFiller = stringFiller + fillStr;
+      return s + stringFiller.substring(0, fillLen);
+    });
+
+  // 21.1.3.14 String.prototype.padStart( maxLength [ , fillString ] )
+  define(
+    String.prototype, 'padStart',
+    function padStart(maxLength) {
+      var fillString = arguments[1];
+
+      var o = this;
+      // ReturnIfAbrupt(o)
+      var s = String(this);
+      // ReturnIfAbrupt(s)
+      var stringLength = s.length;
+      if (fillString === undefined) var fillStr = '';
+      else fillStr = String(fillString);
+      // ReturnIfAbrupt(fillStr)
+      if (fillStr === '') fillStr = ' ';
+      var intMaxLength = ToLength(maxLength);
+      // ReturnIfAbrupt(intMaxLength)
+      if (intMaxLength <= stringLength) return s;
+      var fillLen = intMaxLength - stringLength;
+      var stringFiller = '';
+      while (stringFiller.length < fillLen)
+        stringFiller = stringFiller + fillStr;
+      return stringFiller.substring(0, fillLen) + s;
+    });
+
+}(this));
diff --git a/es2017.md b/es2017.md
@@ -0,0 +1,14 @@
+# ECMAScript 2017 Polyfill
+
+[script](es2017.js) -
+[unit tests](https://inexorabletash.github.io/polyfill/tests/es2017.html)
+
+This assumes ES2016, so use [es5.js](es5.js), [es6.js](es6.js) and [es2016.js](es2016.js) for older browsers (IE9-).
+
+[ECMAScript Standard](http://www.ecma-international.org/ecma-262/)
+
+* `Object.entries()` [ref](https://tc39.github.io/ecma262/#sec-object.entries)
+* `Object.values()` [ref](https://tc39.github.io/ecma262/#sec-object.values)
+* `Object.getOwnPropertyDescriptors` [ref](https://tc39.github.io/ecma262/#sec-object.getownpropertydescriptors)
+* `String.prototype.padEnd()` [ref](https://tc39.github.io/ecma262/#sec-string.prototype.padend)
+* `String.prototype.padStart()` [ref](https://tc39.github.io/ecma262/#sec-string.prototype.padstart)