loop benchmarks

loop-bench.js

var a = [];
for (var i = 0; i < 100000; i++) a.push('a');
var o = {};
for (var i = 0; i < 100000; i++) o['key_' + i] = 'a';


(function() {
  var s = Date.now();
  var i = a.length;
  while (i--) {
    var b = a[i];
  }
  console.log('while array:', Date.now() - s);
})();

(function() {
  var s = Date.now();
  var k = Object.keys(o), i = k.length;
  while (i--) {
    var b = o[k[i]];
  }
  console.log('while object:', Date.now() - s);
})();

(function() {
  var s = Date.now();
  var i = a.length - 1;
  do {
    var b = a[i];
  } while (i--);
  console.log('do-while array:', Date.now() - s);
})();

(function() {
  var s = Date.now();
  var k = Object.keys(o), i = k.length-1;
  do {
    var b = o[k[i]];
  } while (i--);
  console.log('do-while object:', Date.now() - s);
})();

(function() {
  var s = Date.now();
  for (var i = 0, l = a.length; i < l; i++) {
    var b = a[i];
  }
  console.log('for array:', Date.now() - s);
})();

(function() {
  var s = Date.now();
  var k = Object.keys(o);
  for (var i = 0, l = k.length; i < l; i++) {
    var b = o[k[i]];
  }
  console.log('for object:', Date.now() - s);
})();

(function() {
  var s = Date.now();
  a.forEach(function(v) {
    var b = v;
  });
  console.log('forEach array:', Date.now() - s);
})();

(function() {
  var s = Date.now();
  Object.keys(o).forEach(function(k) {
    var b = o[k];
  });
  console.log('forEach object:', Date.now() - s);
})();


(function() {
  var s = Date.now();
  for (var k in o) {
    var b = o[k];
  };
  console.log('for...in object:', Date.now() - s);
})();


(function() {
  var s = Date.now();
  for (var k in o) {
    if (o.hasOwnProperty(k)) var b = o[k];
  };
  console.log('for...in wrapper object:', Date.now() - s);
})();

(function() {
  var s = Date.now();
  for (var k in a) {
    var b = a[k];
  };
  console.log('for...in array:', Date.now() - s);
})();

(function() {
  var s = Date.now();
  for (var k in a) {
    if (a.hasOwnProperty(k)) var b = a[k];
  };
  console.log('for...in wrapper array:', Date.now() - s);
})();