Sometimes you need to modify your HTML to work around differences in browsers and operating systems. And sometimes you need to do something that HTML just doesn't do ...

JavaScript can run on any device that has a JavaScript Runtime Environment (JRE). The heart of the JRE is the JS Engine — a piece of software (not hardware) that interprets and executes JavaScript.

. The section on media elements provides detailed coverage of the and elements. Like the first chapter, Chapter 2 focuses mostly on a general web concept, in this case Cascading Style Sheets (CSS).

setTimeout guarantees a minimum delay — not an exact one. The callback cannot run until the Call Stack is empty, so a busy main thread makes timers lie. JavaScript is single-threaded — there is only ...