speedTest.js

var arr = [1,2,3,4,5,6,7,8,9,10,1,2,3,4,5,6,7,8,9,10,1,2,3,4,5,6,7,8,9,10]
  , i
  , sum
  ;

console.time("while");
  i = arr.length;
  sum = 0;
  
  while (i--)
    sum+=arr[i]
console.timeEnd("while");

console.time("for");
  length = arr.length;
  i = 0;
  sum = 0;
  
  for (; i < length; i += 1)
    sum += arr[i];
console.timeEnd("for");

console.time("reduce");
  arr.reduce(function(prev,cur) {
    return prev += cur;
  }, 0);
console.timeEnd("reduce");