SpiderMonkey is the code name for the first-ever JavaScript engine, written by Brendan Eich at Netscape Communications, later released as open source and now maintained by the Mozilla Foundation. SpiderMonkey implements ECMA-262 edition 5 (ECMAScript), along with ECMA-357 (E4X) and several additional features. Even though SpiderMonkey is used in Firefox, it does not itself provide host environments such as Document Object Model (DOM).