for vs forEach (v181)

Revision 181 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.

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;
    };
    
    function each1 (data, iterator) {
        var i,
                length = data.length;
        for (i = 0; i < length; i += 1) {
                iterator(data[i], i, data);
        }
    }
    
    function each2 (data, iterator) {
        var i,
                length = data.length;
        for (i = 0; i < length; ++i) {
                iterator(data[i], i, data);
        }
    }

Teardown


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

Test runner

Ready to run.

Testing in
TestOps/sec
strict 0 comparison
var arr = values,
    length = arr.length;
while (length-- !== 0) {
    add(arr[length], length, arr);
}
ready
for loop, cached length, callback
var arr = values,
    length = arr.length;
while (--length !== -1) {
    add(arr[length], length, arr);
}
ready
for loop, cached length, callback, reduce op
var arr = values,
    length = arr.length;
for (var i = 0; i < length; ++i) {
    add(arr[i], i, arr);
}
ready
new each
each(values, add);
ready
without strict zero comparison
var arr = values,
    length = arr.length;
while (--length) {
    add(arr[length], length, arr);
}
ready
each1
each1(values, add);
ready
each2
each2(values, add);
ready

Revisions

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