for vs forEach (v107)

Revision 107 of this benchmark created on

Description

Is it faster to use the native forEach or just loop with for?

Inspired by Adrian Sutton's tests at: http://www.symphonious.net/2010/10/09/javascript-performance-for-vs-foreach/

This one adds random floating point numbers to see if the loop overhead is significant at all in the face of standard work.

Preparation HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js">
</script>

Setup

var i,
        value,
        length,
        values = [],
        sum = 0,
        context = values;
    
    
    for (i = 0; i < 10000; i++) {
        values[i] = Math.random();
    }
    
    function add(val) {
        sum += val;
    }
    
    if (!Array.prototype.forEach) {
            Array.prototype.forEach = function (fun /*, thisp*/) {
                var len = this.length >>> 0;
                if (typeof fun != "function") {
                    throw new TypeError();
                }
    
                var thisp = arguments[1];
                for (var i = 0; i < len; i++) {
                    if (i in this) {
                        fun.call(thisp, this[i], i, this);
                    }
                }
            };
        }

Teardown


    i = 0;
    value = 0;
    length = 0;
    values = [];
    sum = 0;

Test runner

Ready to run.

Testing in
TestOps/sec
forEach
values.forEach(add);
ready
for loop, inversed
for (i = values.length - 1; i >= 0; i--) {
    sum += values[i];
}
ready
for loop, cached length
var length = values.length;
var i = 0;
for (; i < length; ++i) {
    sum += values[i];
}
ready
for loop, cached length (without var)
length = values.length;
for (i = 0; i < length; i++) {
    sum += values[i];
}
ready
for loop, cached length, callback
length = values.length;
for (i = 0; i < length; i++) {
    add(values[i], i, values);
}
ready
for loop, cached length, callback.call
length = values.length;
for (i = 0; i < length; i++) {
    add.call(context, values[i], i, values);
}
ready
$.each
$.each(values, function(key, value) {
    sum += value;
});
ready
for ... in
for (i in values) {
    sum += values[i];
}
ready
for loop, reverse, decrement condition
for (i = values.length; i--;) {
    sum += values[i];
}
ready
for loop, reverse, pre-decrement
for (i = values.length - 1; i >= 0; --i) {
    sum += values[i];
}
ready
for loop, assignment condition
for (i = 0; (value = values[i]) !== undefined; i++) {
    sum += value;
}
ready
for loop, assignment condition, reversed
for (i = values.length - 1; (value = values[i]) !== undefined; i--) {
    sum += value;
}
ready
for loop, assignment condition, callback
for (i = 0; (value = values[i]) !== undefined; i++) {
    add(value, i, values);
}
ready
for loop, assignment condition, callback.call
for (i = 0; (value = values[i]) !== undefined; i++) {
    add.call(context, value, i, values);
}
ready

Revisions

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