Iterating over array

perf.js

// Benchmarking summation of array

var a = [];
for(var i = 0; i < 100; ++i) a.push(Math.random());

this.group(
  "Iterations",
  function classic(){
    for(var sum = 0, i = 0, l = a.length; i < l; ++i){ sum += a[i]; }
  },
  function short(){
    for(var sum = 0, i = 0, l = a.length; i < l; sum += a[i++]);
  },
  function forEach(){ var sum = 0; a.forEach(function(x){ sum += x; }); },
  function reduce(){ var sum = a.reduce(function(a, b){ return a + b; }, 0); },
  function reduceRight(){ var sum = a.reduceRight(function(a, b){ return a + b; }, 0); }
);

Benchmark it with http://www.perfjs.com/