SUMMARY

JavaScript is a scripting language designed to interact with web pages and is made up of the following three distinct parts:

• ECMAScript, which is defined in ECMA-262 and provides the core functionality
• The Document Object Model (DOM), which provides methods and interfaces for working with the content of a web page
• The Browser Object Model (BOM), which provides methods and interfaces for interacting with the browser

There are varying levels of support for the three parts of JavaScript across the five major web browsers (Internet Explorer, Firefox, Chrome, Safari, and Opera). Support for ECMAScript 5 is generally good across all browsers, and support for ECMAScript 6 and 7 is growing. Support for the DOM varies, but Level 3 compliance is increasingly normative. The BOM, codified in HTML5, can vary from browser to browser, though there are some commonalities that are assumed to be available.