Polyfills the `requestAnimationFrame` function for all browsers.

polyfill-request-animation-frame.js

(function(context) {
    var exts = ['', 'webkit', 'moz', 'o', 'ms'];
    
    function lookup(name) {
        var n, i;
        for (i in exts) {
            n = lcfirst(exts[i] + ucfirst(name));
            if (context[n]) return n;
        }
        return false;
    }
    
    function lcfirst(str) { return str[0].toLowerCase() + str.slice(1); }
    function ucfirst(str) { return str[0].toUpperCase() + str.slice(1); }
    
    function polyfill(name, func) {
        var _native = lookup(name); 
        if (!_native) context[name] = func;
        else context[name] = context[_native];
    }
    
    // ----[ requestAnimationFrame ]----
    var lastFrame = 0;
    polyfill('requestAnimationFrame', function(callback) {
        setTimeout(callback, 16);
        return lastFrame++;
    });
    
})(this);

It turns out that 'native' is a reserved keyword in js. This code works ok in browser, but things like jslint and yui compressor are throwing errors about variable with that name.

Good catch, I'll just underscore it.