copy-paste using javascript

I have text in JS variable and I want that to be copied in clipboard on a button's cl开发者_开发知识库ick. I need this in Javascript and code must not be browser-specific.

ZeroClipboard works fully within the browser's security restrictions. It uses Flash to copy to the clipboard, accessing a Flash movie from JavaScript. To work around Flash's own security limitation, it must be overlaid on top of some element of your page (e.g. a button) that the user will have to click. Read its instructions page for more details.