es5-shim

What is es5-shim?

The es5-shim package is a JavaScript library that provides compatibility shims so that legacy JavaScript engines behave as closely as possible to ECMAScript 5 (ES5). This is particularly useful for supporting older browsers that do not implement all ES5 features natively.

What are es5-shim's main functionalities?

Array methods

Provides ES5 array methods like map, filter, and reduce which might not be available in older JavaScript engines.

[1, 2, 3].map(function(n) { return n + 1; })

Function.prototype.bind

Implements Function.prototype.bind, allowing functions to have their this value and initial arguments pre-set.

var boundFunc = function(a, b) { return a + b; }.bind(null, 1); boundFunc(2);

Object methods

Adds missing Object methods such as keys, which returns an array of a given object's own enumerable property names.

Object.keys({a: 1, b: 2})

String methods

Includes String.prototype methods like trim, which removes whitespace from both ends of a string.

'hello'.trim()

Date methods

Provides shims for Date methods like now, which returns the number of milliseconds elapsed since January 1, 1970 00:00:00 UTC.

Date.now()

Other packages similar to es5-shim

core-js

A modular standard library for JavaScript, core-js includes polyfills for ECMAScript up to 2021. It covers more features than es5-shim, including promises, symbols, collections, iterators, typed arrays, and many other features of ECMAScript 2015 and beyond.

babel-polyfill

Part of Babel's suite, babel-polyfill includes a custom regenerator runtime and core-js. This package is more comprehensive than es5-shim as it supports new ES6 features and beyond, making it suitable for applications needing high compatibility with new ECMAScript standards.

README

Provides compatibility shims so that legacy JavaScript engines behave as closely as possible to ES5.