for vs forEach, including uncached length for worst-case (v202)

Revision 202 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. And, a worst-case for loop with an un-cached length counter.

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 < 10000; 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
for loop, un-cached length, callback
var arr = values;
for (var i = 0; i < arr.length; i++) {
    add(arr[i], i, arr);
}
ready
for loop, cached length in loop,
var arr = values;
for (var i = 0, n = arr.length; i < n; i++) {
    add(arr[i], i, arr);
}
ready

Revisions

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