JavaScript is the language used on web sites to control your browser. It’s not to be confused with the similarly named language “Java”. They’re two completely different animals.
JavaScript is an interpreted language, meaning there’s a JavaScript engine that reads the JavaScript source code at run time and interprets it, line by line, and takes action then. This is unlike compiled languages like C or C++, which are converted from source code to machine code, for quick execution. Since JavaScript is an interpreted language, it is fairly slow in comparison to compiled languages.
But, the fact that it isn’t compiled into machine code before it’s sent to your browser, means that it can run on just about any hardware and any operating system from Windows, to Mac, to Linux, to cell phones. It sacrifices speed for portability.
JavaScript’s main purpose is to control the user interface of web pages. JavaScript code can animate items across your browser, can switch focus to a specific control, can validate data you enter onto a web form before you submit it, can change colors of page elements, and a whole plethora of other things.
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