Question: What is JavaScript?
Answer: JavaScript is a scripting language designed for adding interactivity to Web pages. The language was first implemented by Netscape Communications in Netscape Navigator 2 beta (1995). JavaScript is different from the Java language (developed at Sun Microsystems). However, the two languages can interoperate well.
Client-side JavaScript programs, or scripts, are usually embedded directly in HTML source of Web pages. (Note: There is also server-side JavaScript, but it's beyond the scope of this FAQ collection.) Depending on the Web developer's intent, script code may run when the user opens the Web page, clicks or drags some page element with the mouse, types something on the keyboard, submits a form, or leaves the page.
In most existing implementations, JavaScript is an interpreted language. This means that scripts execute without preliminary compilation, i.e. without conversion of the script text into system-dependent machine code. The user's browser interprets the script, that is, analyzes and immediately executes it. JavaScript is supported by the following browsers:
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