ECMAScript 5 In code examples

es5-features.js

/**
 * Strict mode
 *  Opt in to a restricted variant of JavaScript.
 */
'use strict';
(function() { 'use strict'; });

/**
 * Array.prototype.forEach()
 *  Executes a provided function once per array element.
 *  thisArg: the value to use as this when executing callback.
 */
['aap', 'noot', 'mies'].forEach(function(value, index, arr) {
    console.log('a[' + index + '] = ' + value);
}, thisArg);

/**
 * Array.prototype.map()
 *  Creates a new array by calling a function for every item.
 *  thisArg: the value to use as this when executing callback.
 */
['3.14', '2.71'].map(function(value, index, arr) {
    return parseFloat(value);
}, thisArg);

/**
 * Array.prototype.filter()
 *  Filters items of an array.
 *  thisArg: the value to use as this when executing callback.
 */
[0, 1, 2, 3, 4].filter(function(value, index, arr) {
    return Math.round(Math.random());
}, thisArg);

/**
 * Array.prototype.reduce()
 * Array.prototype.reduceRight()
 *  Iteratively reduce an array to a single value.
 *  Reduce works ltr, reduceRight works rtl.
 */
[0, 1, 2, 3, 4].reduce(function(prev, next, index, arr) {
    return prev + next;
});
[0, 1, 2, 3, 4].reduceRight(function(prev, next, index, arr) {
    return prev + next;
});

/**
 * Array.prototype.every()
 * Array.prototype.some()
 *  Test whether every/some items passes a test.
 *  thisArg: the value to use as this when executing callback.
 */
var fn = function(value, index, arr) {
    return !!value;
};
[1, 2, 0, 4, 5].every(fn, thisArg);
[1, 2, 3, 0, 5].some(fn, thisArg);

/**
 * Array.prototype.indexOf()
 * Array.prototype.lastIndexOf()
 *  Find the index of the item that equals a value.
 */
[0, 2, 2, 4, 6].indexOf(6);
[0, 1, 1, 3, 4].lastIndexOf(1);

/**
 * Array.isArray()
 *  Checks if a variable is a real array.
 */
Array.isArray({length: 2, 0: 'aap', 1: 'noot'});

/**
 * Function.prototype.bind()
 *  Proxy a function with given context and arguments.
 */
(function(arg) {
    return 'aap ' + this.value + ' mies ' + arg;
}.bind({value: 'noot'}))('wim');

/**
 * Object.preventExtensions()
 * Object.isExtensible()
 *  Prevents future property additions from occurring,
 *  cannot be undone.
 */
var zus = {jet: 'teun'};
Object.preventExtensions(zus);
Object.isExtensible(zus);
zus.vuur = 'gijs'; // no-op

/**
 * Object.seal()
 * Object.isSealed()
 *  Prevents any changes to properties or descriptors of the object,
 *  values can still be changed.
 */
var mies = Object.seal({wim: 'zus'});
Object.isSealed(mies);

/**
 * Object.freeze()
 * Object.isFrozen()
 *  Prevents any changes to the object.
 */
var wim = Object.freeze({zus: 'jet'});
Object.isFrozen(wim);

/**
 * JSON
 *  parse() — Parse a string as JSON.
 *  stringify() — Convert a value to JSON.
 */
JSON.parse('[1, 2, 3, 4]');
JSON.stringify({aap: 'monkey'});

/**
 * Date object
 *  now() — Get current timestamp
 *  parse() — Now accepts subset ISO 8601 formatted dates
 *  toJSON() — Get JSON representation
 *  toISOString() — Get ISO 8601 formatted date
 */
Date.now();
Date.parse('2013-08-05');
(new Date()).toJSON();
(new Date()).toISOString();

/**
 * Property access on strings
 */
var str = 'aap noot mies wim zus jet teun vuur gijs lam';
str[9] + str[1] + str[2];

/**
 * String.prototype.trim()
 *  Trim whitespace of the beginning and end of a string.
 */
'   aap noot mies   '.trim();

/**
 * Zero-width chars in identifiers
 */
var $\u200c = 'a',
    teun = {_\u200d: 'vuur'};

/**
 * Reserved words as property names
 */
var jet = {if: 3, throw: .14};

/**
 * Multiline string literals
 */
var leesplankje = 'aap \
noot mies';

/**
 * `with` keyword is now deprecated
 */
with ({aap: 'noot'}) {
    console.log(aap);
}

/**
 * Global objects are now read only
 *  Both statements are a no-op.
 */
Infinity = 42;
var NaN = 'aap', undefined = 'noot';

/**
 * Removed object properties
 *  Both statements return undefined.
 */
({}).__parent__;
({}).__count__;

todo.js

/**
 * Resources:
 *  http://kangax.github.io/es5-compat-table/
 *  https://github.com/kriskowal/es5-shim/blob/master/es5-shim.js
 *  http://ejohn.org/blog/ecmascript-5-objects-and-properties/
 *  http://www.jayway.com/2011/04/05/what-is-new-in-ecmascript-5/
 */

/**
 * Object.create()
 *  Create a new object, specifying prototype and properties.
 *  @todo example
 */
Object.create();

Object.clone();

Object.defineProperty();
Object.defineProperties();
Object.getOwnPropertyDescriptor();
Object.getPrototypeOf();

Object.keys();
Object.getOwnPropertyNames();

// Getters & Setters as property initializer
// Getters & Setters as named properties

Number.prototype.toFixed();
toObject();
toInteger();
toPrimitive();
isPrimitive();

/**
 * Property descriptor
 *  writable — Can the value be changed?
 *  enumerable — Will it appear in for-in and Object.keys()
 *  configurable — Can the property be removed?
 *  get/set —
 *  @todo finish
 */
var myÜberDescriptor = {
    writable: false,
    enumerable: true,
    configurable: false,
    get: function(v) {
        return this.noot;
    },
    set: function(v) {
        this.noot = v;
    }
};