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Provides compatibility shims so that legacy JavaScript engines behave asclosely as possible to ECMAScript 6 (Harmony).

HTML version of the final ECMAScript 6 spec

If you want to use it in browser:

• Just includees6-shim before your scripts.
• Includees5-shim especially if your browser doesn't support ECMAScript 5 - but every JS engine requires thees5-shim to correct broken implementations, so it's strongly recommended to always include it. Additionally,es5-shim should be loaded beforees6-shim.

Fornode.js,io.js, or anynpm-managed workflow (this is the recommended method):

npm install es6-shim

Alternative methods:

• component install paulmillr/es6-shim if you’re usingcomponent(1).
• bower install es6-shim if you’re usingBower.

In both browser and node you may also want to includeunorm; see theString.prototype.normalize section for details.

• Map (requires ES5 property descriptor support) (a standalone shim is also available)
• Set (requires ES5 property descriptor support) (a standalone shim is also available)
• Promise
• String:
  • fromCodePoint() (a standalone shim is also available)
  • raw() (a stanadlone shim is also available)
• String.prototype:
  • codePointAt() (a standalone shim is also available)
  • endsWith() (a standalone shim is also available)
  • includes() (a standalone shim is also available)
  • repeat() (a standalone shim is also available)
  • startsWith() (a standalone shim is also available)
• RegExp:
  • new RegExp, when given a RegExp as the pattern, will no longer throw when given a "flags" string argument. (requires ES5)
• RegExp.prototype:
  • flags (requires ES5) (a standalone shim is also available)
  • [Symbol.match] (requires nativeSymbols)
  • [Symbol.replace] (requires nativeSymbols)
  • [Symbol.search] (requires nativeSymbols)
  • [Symbol.split] (requires nativeSymbols)
  • toString
• Number:
  • binary and octal literals:Number('0b1') andNumber('0o7')
  • EPSILON (a standalone shim is also available)
  • MAX_SAFE_INTEGER (a standalone shim is also available)
  • MIN_SAFE_INTEGER (a standalone shim is also available)
  • isNaN() (a standalone shim is also available)
  • isInteger() (a standalone shim is also available)
  • isSafeInteger()(a standalone shim is also available)
  • isFinite() (a standalone shim is also available)
  • parseInt() (a standalone shim is also available)
  • parseFloat()
• Array:
  • from() (a standalone shim is also available)
  • of() (a standalone shim is also available)
• Array.prototype:
  • copyWithin() (a standalone shim is also available)
  • entries() (a standalone shim is also available)
  • fill()
  • find() (a standalone shim is also available)
  • findIndex() (a standalone shim is also available)
  • keys() (a standalone shim is also available)
  • values() (a standalone shim is also available)
  • indexOf() (ES6 errata) (a standalone shim is also available)
• Object:
  • assign() (a standalone shim is also available)
  • is() (a standalone shim is also available)
  • keys() (in ES5, but no longer throws on non-object non-null/undefined values in ES6) (a standalone shim is also available
  • setPrototypeOf() (IE >= 11)
• Function.prototype:
  • name (es6-sham, covers IE 9-11) (a standalone shim is also available
• Math:
  • acosh() (a standalone shim is also available)
  • asinh()
  • atanh() (a standalone shim is also available)
  • cbrt() (a standalone shim is also available)
  • clz32() (a standalone shim is also available)
  • cosh()
  • expm1()
  • fround() (a standalone shim is also available)
  • hypot()
  • imul() (a standalone shim is also available)
  • log10() (a standalone shim is also available)
  • log1p() (a standalone shim is also available)
  • log2()
  • sign() (a standalone shim is also available)
  • sinh()
  • tanh()
  • trunc()

Math functions’ accuracy is 1e-11.

• Reflect

  • apply() (a standalone shim is also available)
  • construct()
  • defineProperty()
  • deleteProperty()
  • get()
  • getOwnPropertyDescriptor()
  • getPrototypeOf() (a standalone shim is also available)
  • has()
  • isExtensible()
  • ownKeys() (a standalone shim is also available)
  • preventExtensions()
  • set()
  • setPrototypeOf()

• Symbol (only if it already exists)

  • match (and correspondingString#match,String#startsWith,String#endsWith,String#includes,RegExp support)
  • replace (and correspondingString#replace support)
  • search (and correspondingString#search support)
  • split (and correspondingString#split support)

Well-known symbols will only be provided if the engine already hasSymbol support.

• String.prototype Annex B HTML methods (a standalone shim is also available)
  • anchor()
  • big()
  • blink()
  • bold()
  • fixed()
  • fontcolor()
  • fontsize()
  • italics()
  • link()
  • small()
  • strike()
  • sub()
  • sup()

These methods are part of "Annex B", which means that although they are a defacto standard, you shouldn't use them. None the less, thees6-shim provides them and normalizes their behavior across browsers.

TheMap,Set, andPromise implementations are subclassable.You should use the following pattern to create a subclass in ES5 which will continue to work in ES6:

require('es6-shim');functionMyPromise(exec){varpromise=newPromise(exec);Object.setPrototypeOf(promise,MyPromise.prototype);// ...returnpromise;}Object.setPrototypeOf(MyPromise,Promise);MyPromise.prototype=Object.create(Promise.prototype,{constructor:{value:MyPromise}});

Including a proper shim forString.prototype.normalize would increase the size of this library by a factor of more than 4.So instead we recommend that you install theunorm package alongsidees6-shim if you needString.prototype.normalize.Seepaulmillr#134 for more discussion.

It is not possible to implement WeakMap in pure javascript.Thees6-collections implementation doesn't hold values strongly, which is critical for the collection.es6-shim decided to not include an incorrect shim.

WeakMap has very unusual use-cases, so you probably won't need it at all (use simpleMap instead).

require('es6-shim');varassert=require('assert');assert.equal(true,'abc'.startsWith('a'));assert.equal(false,'abc'.endsWith('a'));assert.equal(true,'john alice'.includes('john'));assert.equal('123'.repeat(2),'123123');assert.equal(false,NaN===NaN);assert.equal(true,Object.is(NaN,NaN));assert.equal(true,-0===0);assert.equal(false,Object.is(-0,0));varresult=Object.assign({a:1},{b:2});assert.deepEqual(result,{a:1,b:2});assert.equal(true,isNaN('a'));assert.equal(false,Number.isNaN('a'));assert.equal(true,Number.isNaN(NaN));assert.equal(true,isFinite('123'));assert.equal(false,Number.isFinite('123'));assert.equal(false,Number.isFinite(Infinity));// Tests if value is a number, finite,// >= -9007199254740992 && <= 9007199254740992 and floor(value) === valueassert.equal(false,Number.isInteger(2.4));assert.equal(1,Math.sign(400));assert.equal(0,Math.sign(0));assert.equal(-1,Math.sign(-400));varfound=[5,10,15,10].find(function(item){returnitem/2===5;});assert.equal(10,found);varfoundIndex=[5,10,15,10].findIndex(function(item){returnitem/2===5;});assert.equal(1,foundIndex);// Replacement for `{}` key-value storage.// Keys can be anything.varmap=newMap([['Bob',42],['Foo','bar']]);map.set('John',25);map.set('Alice',400);map.set(['meh'],555);assert.equal(undefined,map.get(['meh']));// undefined because you need to use exactly the same object.map.delete('Alice');map.keys();map.values();assert.equal(4,map.size);// Useful for storing unique items.varset=newSet([0,1]);set.add(2);set.add(5);assert.equal(true,set.has(0));assert.equal(true,set.has(1));assert.equal(true,set.has(2));assert.equal(false,set.has(4));assert.equal(true,set.has(5));set.delete(5);assert.equal(false,set.has(5));// Promises, see// http://www.slideshare.net/domenicdenicola/callbacks-promises-and-coroutines-oh-my-the-evolution-of-asynchronicity-in-javascript// https://github.com/petkaantonov/bluebird/#what-are-promises-and-why-should-i-use-themPromise.resolve(5).then(function(value){assert.equal(value,5);if(value)thrownewError('whoops!');// do some stuffreturnanotherPromise();}).catch(function(e){assert.equal(e.message,'whoops!');assert.equal(true,einstanceofError);// any errors thrown asynchronously end up here});

• Object.setPrototypeOf /Reflect.setPrototypeOf
  • Note that null objects (Object.create(null), eg, an object withnull as its[[Prototype]]) can not have their[[Prototype]] changed except via a nativeObject.setPrototypeOf.
• Well-knownSymbols
  • In order to make them work cross-realm, these are created with the globalSymbol registry viaSymbol.for. This does not violate the spec, but it does mean thatSymbol.for('Symbol.search') === Symbol.search will betrue, which it would not by default in a fresh compliant realm.

The project was initially based on es6-shim by Axel Rauschmayer.