performance.js

var max = 10000
var pi = Math.PI;

var a = new Array(max); 
console.time('native'); 
for (var i = 0, len = a.length; i < len; i++) {
  a[i] = pi;
};
console.timeEnd('native'); 

var b = new Array(max);
console.time('each'); 
$.each(b, function(k, v) {
  b[k] = pi;
});
console.timeEnd('each');  

// Use http://code.jquery.com/jquery-1.8.2.min.js
// native: 58ms
// each: 40ms