KJS is KDE's ECMAScript-JavaScript engine that was originally developed for the KDE project's Konqueror web browser by Harri Porten in 2000.On June 13, 2002, Maciej Stachowiak announced on a mailing list that Apple was releasing JavaScriptCore, a framework for Mac OS X that was based on KJS. Through the WebKit project, JavaScriptCore has since evolved into SquirrelFish Extreme, a JavaScript engine that compiles JavaScript into native machine code.