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ECMAScript 6 Polyfill

script - unit tests

The standardization of ES6 is currently in progress. This will attempt to track the evolving spec, so may change at any time. This assumes ES5, so use es5.js for older browsers (IE9-).

In the ES6 Drafts:

Fundamental Objects

  • Object: assign(), is(), setPrototypeOf()
  • Symbol: Symbol(description), Symbol.for(), Symbol.keyFor(), Symbol.iterator, Symbol.toStringTag
    • No security, just creates an object with a unique string representation. typeof Symbol() will incorrectly report "object" but Symbol() instanceof Symbol will return true
  • Not supported: Function.prototype.toMethod()

Numbers and Dates

  • Number: EPILON, isFinite(), isInteger(), isNaN(), isSafeInteger(), MAX_SAFE_INTEGER, MIN_SAFE_INTEGER, parseFloat(), parseInt()
  • Math: acosh(), asinh(), atanh(), cbrt(), clz32(), cosh(), expm1(), fround, hypot(), imul(), log1p(), log10(), log2(), sign(), sinh(), tanh(), trunc()

Text Processing

Indexed Collections

  • Array: from(), of()
  • Array prototype: copyWithin(), entries(), fill(), find(), findIndex(), keys(), values(), [@@iterator]()
  • TypedArray - for browsers without native support (IE9-) include typedarray.js
  • %TypedArray% prototype: from(), of()
  • %TypedArray% prototype: copyWithin(), entries(), every(), fill(), filter(), find(), findIndex(), forEach(), indexOf(), join(), keys(), lastIndexOf(), map(), reduce(), reduceRight(), reverse(), slice(), some(), sort(), values(), [@@iterator]()

Keyed Collections

  • Map: clear(), delete(), entries(), forEach(), get(), keys(), has(), set(), size, values(), [@@iterator]()
  • Set: add(), clear(), delete(), entries(), forEach(), has(), size, values(), [@@iterator]()
  • WeakMap: clear(), delete(), get(), has(), set()
  • WeakSet: add(), clear(), delete(), has()
    • WeakMap and WeakSet are intrusive and modify the valueOf property of keys

Asynchronous Programming

  • Promise: p = new Promise(), Promise.resolve(), Promise.reject(), Promise.cast(), Promise.race(), Promise.all(), p.then(), p.catch()
  • promises spec

Syntax Helpers

  • forOf(o, function(i) { ... }) - since for (i of o) { ... } can't be polyfilled. Uses iterators, so works with arrays, maps, sets, and strings, via implicit @@iterator and explicit iterators returned by keys/values/entries methods and functions.

See also: uate - ES5 "tagged template strings"

Typed Arrays

script - unit tests - spec

Originally specified separately, Typed Arrays are now included in ES6.

  • ArrayBuffer
  • Uint8Array, Int8Array, Uint16Array, Int16Array, Uint32Array, Int32Array, Float32Array, Float64Array
  • DataView

Creating index getter/setters (i.e. array[0], array[1], etc) is slow and consumes significant memory. Arrays larger than 100k entries will be too slow to initialize in most cases so an upper limit is placed on the size of arrays and exception is thrown on construction.