for vs forEach (v52)

Revision 52 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="http://code.jquery.com/jquery-1.8.2.min.js">
</script>

Setup

var i,
        value,
        length,
        values = [],
        sum = 0,
        context = values;
    
    
    for (i = 0; i < 7; i++) {
        values[i] = Math.random();
    }
    
    function add(val) {
        sum += val;
    }
    function addEach(k, val) {
        sum += val;
    }
    
    var toString = Object.prototype.toString;
    
    function isArray(obj) {
        return toString.call(obj) === '[object Array]';
    }
    
    function isObject(obj) {
        return toString.call(obj) === '[object Object]';
    }
    
    function isString(obj) {
        return toString.call(obj) === '[object String]';
    }
    
    function each(obj, iterator) {
        var key, length;
        if (!obj) {
                return;
        }
        length = obj.length;
    
        if (isArray(obj) || isString(obj)) {
                for(key = 0; key < length; key += 1) {
                        iterator(obj[key], key, obj);
                }
                return obj;
        }
    
        if (isObject(obj)) {
                for(key in obj) {
                        if (obj.hasOwnProperty(key)) {
                                iterator(obj[key], key, obj);
                        }
                }
                return obj;
        }
    
        return obj;
    };

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, cached length, callback
var arr = values,
    length = arr.length;
for (var i = 0; i < length; i++) {
    add(arr[i], i, arr);
}
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, addEach);
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
native map function
values.map(add);
ready
new each
each(values, add);
ready

Revisions

You can edit these tests or add more tests to this page by appending /edit to the URL.