ECMAScript Versions and Features

Introduction

Over the years, multiple ECMAScript versions have been released with various features. These features are outlined here to show the impact on JavaScript and the changes over the years.

ECMAScript 5

ECMAScript 5, released in 2009, is known as ES5 or ECMAScript 2009. Some features released in ES5 we already used in the course:

• Array methods released in ES5 are:
  • Array.isArray()
  • Array.map()
  • Array.reduce()
  • Array.filter()
  • Array.forEach()
• JSON support via JSON object along with the following methods:
  • JSON.parse()
  • JSON.stringify()
• Object support via Object object by introducing the following methods:
  • Object.create()
  • Object.keys()
  • Object.getPrototypeof()
• New methods for Date object:
  • Date.now()

Beyond these features, ES5 lets users use strict mode, which creates restrictions to avoid errors. For instance, it does not allow undeclared variables. Before ES5, there were no such restrictions.