for-in versus Object.keys(..).forEach(..) (v30)

Revision 30 of this benchmark created on

Description

Testing if the perf hit for Object.keys(..).forEach(..) is enough to matter as compared to for-in.

Preparation HTML

<script>
// pre-ES5 polyfill for Object.keys()
Object.keys=Object.keys||function(o,k,r){r=[];for(k in o)r.hasOwnProperty.call(o,k)&&r.push(k);return r}

// pre-ES5 polyfill for Array.prototype.forEach()
Array.prototype.forEach||(Array.prototype.forEach=function(a,b){for(var c=0,d=this.length;d>c;++c)a.call(b,this[c],c,this)});


// object with 10 keys in it
var obj = {
   a: 0,
   b: 1,
   c: 2,
   d: 3,
   e: 4,
   f: 5,
   g: 6,
   h: 7,
   i: 8,
   j: 9
};

delete obj.a; //force deoptimization

var tmp;
</script>

Setup

tmp = "";

Test runner

Ready to run.

Testing in
TestOps/sec
for-in
var x = 0;
for (var key in obj) {
  x += obj[key];
}
ready
Object.keys(..).forEach(..)
var x = 0;
Object.keys(obj).forEach(function(key) {
  x += obj[key];
});
ready
Object.keys for loop
var x = 0;
var keys = Object.keys(obj);
for (var i = 0, len = keys.length; i < len; i++) {
  x += obj[keys[i]];
};
ready

Revisions

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