for vs forEach (v240)

Revision 240 of this benchmark created by Ken 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;
    }
    
    // custom forEach
    Array.prototype.forEach2 = function(fn, c) {
    
        //if (this === void 0 || this === null || typeof fn !== 'function') throw new TypeError;
    
        var t = Object(this),
                len = t.length >>> 0,
                nc = (c === void 0 || c === null);
    
        for (var i = 0; i < len; i++) {
                if (i in t) {
                        if (nc) {
                                fn(t[i], i, t)
                        }
                        else {
                                fn.call(c, t[i], i, t)
                        }
                }
        }
    };

Teardown


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

Test runner

Ready to run.

Testing in
TestOps/sec
forEach
values.forEach(function(val) {
    sum += val;
});
ready
for loop, simple
for (i = 0; i < values.length; i++) {
    sum += values[i];
}
ready
for loop, cached length
for (i = 0; i < values.length; sum += values[i], i++) {
  
}
ready
for loop, reverse
for (i = values.length - 1; i >= 0; 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; value = values[i]; 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
custom forEach
values.forEach2(function(val) {
    sum += val;
});
ready

Revisions

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