Add samples for ES6 Computed Property Names
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Addy Osmani
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ES6 Computed Property Names
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===
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<!doctype html>
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<!--
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Copyright 2015 Google Inc. All Rights Reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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<html lang="en">
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<head>
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<meta charset="utf-8">
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<meta http-equiv="X-UA-Compatible" content="IE=edge">
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<meta name="description" content="Sample illustrating the use of Computed Property Names (ES6).">
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<meta name="viewport" content="width=device-width, initial-scale=1">
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<title>Computed Property Names (ES6) Sample</title>
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<meta name="mobile-web-app-capable" content="yes">
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<link rel="icon" sizes="192x192" href="../images/touch/chrome-touch-icon-192x192.png">
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<meta name="apple-mobile-web-app-title" content="Computed Property Names (ES6) Sample">
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<meta name="apple-mobile-web-app-capable" content="yes">
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<meta name="apple-mobile-web-app-status-bar-style" content="black">
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<link rel="apple-touch-icon-precomposed" href="../images/apple-touch-icon-precomposed.png">
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<meta name="msapplication-TileImage" content="images/touch/ms-touch-icon-144x144-precomposed.png">
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<meta name="msapplication-TileColor" content="#3372DF">
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<link rel="icon" href="../images/favicon.ico">
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<link rel="stylesheet" href="../styles/main.css">
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</head>
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<body>
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<h1>Computed Property Names (ES6) Sample</h1>
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<!--
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<p>Available in <a href="http://www.chromestatus.com/feature/PLACEHOLDER">Chrome PLACEHOLDER+</a></p>
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-->
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<p>ES6 Computed property names allow you to dynamically create property names using an expression in brackets (<code>[ ]</code>)
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similar to <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Property_Accessors">property accessors</a>.
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Below, computed property names are demonstrated using Object Literals, ES6 Classes and ES6 Symbols.
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</p>
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<p>Available in Chrome 42 behind the <code>--harmony-computed-property-names</code> flag</p>
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<div class="output">
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<pre id="log"></pre>
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</div>
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<!-- // [START code-block] -->
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<script>
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"use strict";
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function log() {
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document.querySelector('#log').textContent += Array.prototype.join.call(arguments, '') + '\n';
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}
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// Example 1
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log('Using Computed property names in an object literal:');
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var prefix = 'foo';
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var myObject = {
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[prefix + 'bar']: 'hello',
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[prefix + 'baz']: 'world',
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[prefix + prefix.toUpperCase()]: true
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};
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log(myObject['foobar']);
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// -> hello
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log(myObject['foobaz']);
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// -> world
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log(myObject['fooFOO']);
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// -> true
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// Example 2
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log('\nUsing Computed method names in an object literal:');
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var fieldName = "field name";
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var methodName = "method name";
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var O = {
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[fieldName]: "value",
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[methodName]() { log("A method with a computed name was called"); }
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};
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O[methodName]();
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// -> A method with a computed name was called
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// Example 3
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log('\nUsing Computed property names with ES6 Classes:');
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function ID(x) {
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return x;
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}
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class Person {
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getUsername() { return 'ErikArvidsson'}
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['getLastName']() { return 'Arvidsson'; }
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getGroup() { return 'TC39'; }
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[ID('getTeam')]() { return 'Chrome'; }
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}
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log(new Person().getUsername());
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log(new Person().getLastName());
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log(new Person().getGroup());
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log(new Person().getTeam());
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// Example 4
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log('\nUsing Computed property names with ES6 Symbols.');
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log('Define a symbol to use as a property key that will always be unique:');
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let Foo = Symbol();
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var someObject = {
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[Foo]() {
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return 'bar';
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}
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};
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log(someObject[Foo]());
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</script>
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<!-- // [END code-block] -->
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</body>
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</html>
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