requestAnimationFrame, browser prefix detection

raf.js

var rAF = "equestAnimationFrame";

window["r"+rAF] = window["r"+rAF] ||
    window["webkitR"+rAF] ||
    window["mozR"+rAF] ||
    window["msR"+rAF] ||
    window["oR"+rAF];


// A list
[ "r", "webkitR", "mozR", "msR", "oR", "" ].join( rAF + "," ).split( "," )


// Best one yet:
[ "r", "webkitR", "mozR", "msR", "oR" ].reduce(function( p, v ) {
  return window[ v + p ] || p;
}, "equestAnimationFrame");


// Just the prefix
var prefix = [ "r", "webkitR", "mozR", "msR", "oR" ].reduce(function( p, v ) {
  return (window[ v + p ] && v.slice(0, -1)) || p;
}, "equestAnimationFrame");


// Polyfills...
// requestAnimationFrame (from requestAnimationFrame)
// cancelAnimationFrame (from cancelAnimationFrame or cancelRequestAnimationFrame)
(function(window) {
  var time, can, raf, pfx;

  time = 0;
  can = "Cancel";
  raf = "RequestAnimationFrame";
  pfx = ["r", "webkitR", "mozR", "msR", "oR"].reduce(function(p, v) {
    return (window[v + p] && v.slice(0, -1)) || p;
  }, raf.slice(1));

  window.requestAnimationFrame = window[pfx + raf] || function(callback, element) {
    var now, callAt;
    now = +new Date();
    callAt = Math.max(0, 16 - (now - time));
    time = now + callAt;
    return setTimeout(function() {
      callback(time);
    }, callAt);
  };

  window.cancelAnimationFrame = window[pfx + can + raf] ||
    window[pfx + raf.replace(raf.slice(0, 7), can)] || function(id) {
    clearTimeout(id);
  };
}(this));



["r","webkitR","mozR","msR","oR"].reduce(function(p, v) { return window[v + p] || p; }, "equestAnimationFrame");




// Alternate approach ideas

var suffix = "equestAnimationFrame",
  rAF = [ "r", "webkitR", "mozR", "msR", "oR" ].filter(function( val ) {
    return val + suffix in window;
  })[ 0 ] + suffix;
/*
var suffix="equestAnimationFrame",rAF=["r","webkitR","mozR","msR","oR"].filter(function(a){return a+suffix in window})[0]+suffix;

Original Size:  179 bytes (164 bytes gzipped)
Compiled Size:  129 bytes (131 bytes gzipped)
Saved 27.93% off the original size (20.12% off the gzipped size)
*/


var prefix = function(window) {
  var raf = "RequestAnimationFrame",
    idx;

  for (var prop in window) {
    idx = prop.indexOf(raf);

    if (idx > -1) {
      return prop.slice(0, idx);
    }
  }

  return null;
}(this);

/*
var prefix=function(c){var a,b;for(b in c)if(a=b.indexOf("equestAnimationFrame"),a>-1)return b.slice(0,a-1);return null}(this);

Original Size:  232 bytes (184 bytes gzipped)
Compiled Size:  127 bytes (130 bytes gzipped)
Saved 45.26% off the original size (29.35% off the gzipped size)
*/

console.log(
  prefix
);

"Best " + ["s","webkitS","mozS","msS","oS"].reduce(function(p, v) { return window[v + p] || p; }, "him yet");

["r","webkitR","mozR","msR","oR"].reduce(function(p, v) { return window[v + p] || p; }, "equestAnimationFrame");

This trick is awesome.