require of 和 requir for（RequireJS）

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RequireJS is a JavaScript file and module loader. It is optimized for

in-browser use, but it can be used in other JavaScript environments,

like Rhino and Node. Using

a modular script loader like RequireJS will improve the speed and

quality of your code.

IE 6+ .......... compatible ✔

Firefox 2+ ..... compatible ✔

Safari 3.2+ .... compatible ✔

Chrome 3+ ...... compatible ✔

Opera 10+ ...... compatible ✔

Get started then check out the API.