hasOwnProperty performance issue

[ghominejad]

When i call hasOwnProperty some times has good performance and some times 20x slower. for example when i run it 5 times, then 2 times become very slow but 3 times is fast!!! but when i don't use hasOwnProperty then my code always has good performance!

codes :

var cacheobj = {};

console.time('set');
for(var i = 0; i <= 1000000; i++) {
    cacheobj[i + ' a long key a long key '] = i;
}

console.timeEnd('set');
console.time('get');

var val = 0;
for(var i = 0; i <= 1000000; i++) {
    if(cacheobj.hasOwnProperty(i + ' a long key a long key ')) {
        val = cacheobj[i + ' a long key a long key '];
    }
}
console.timeEnd('get');

[ghominejad]

in my real test i generated string keys to avoiding using integer conversion and i sometimes had 25x slower results

var cacheobj = {};
var keys = [];

for(var i = 0; i <= 1000000; i++) {
    keys.push(i + ' a long string key a long string key ');
}

console.time('set');
for(var i = 0; i <= 1000000; i++) {
    var key = keys[i];
    cacheobj[key] = i;
}
console.timeEnd('set');

console.time('get');
var val=0;
for(var i = 0; i <= 1000000; i++) {
    var key = keys[i];
    if(cacheobj.hasOwnProperty(key)) {
        val = cacheobj[key];
    }
}
console.timeEnd('get');

results :
set: 1384ms
get: 372ms

set: 1355ms
get: 9043ms

set: 1472ms
get: 9060ms

set: 1445ms
get: 375ms

set: 1351ms
get: 373ms

[sudheer594]

Surprisingly,
Changing cacheobj.hasOwnProperty(key) to Object.prototype.hasOwnProperty.call(cacheobj,key) improves the situation.

results:

set: 2153ms
get: 674ms
set: 2165ms
get: 703ms
set: 2243ms
get: 975ms
set: 2257ms
get: 641ms
set: 2539ms
get: 659ms

Though , In browser environments cacheobj.hasOwnPropery is working efficiently.

[sudheer594]

If the cacheObj purpose to be a key value pair , we can avoid using objects and instead create a map like this.

function createMap()
    {
        function map(){}
        map.prototype = Object.create(null);

        return new map();
    }

using the createMap method is useful, since you dont have to worry about prototype properties.
Correct me if i am wrong.
referred from https://github.com/shichuan/javascript-patterns

[ghominejad]

Thank you very much, Object.prototype.hasOwnProperty.call solves the problem. but what is the reason?

[sudheer594]

I dont have idea why the performance like this in node.Hope someone with better knowledge on node innerworkings will clarify .
if you want to know why we have to use Object.prototype.hasOwnProperty.call in favor of hasOwnProperty.Here is a article i found to be useful http://jsperf.com/hasownproperty-call-vs-direct/7
for performance Test
http://jsperf.com/hasownproperty-call-vs-direct/7

[CGavrila]

Can't claim to be an expert on the matter, but hasOwnProperty is defined in V8 and its speed is pretty much determined by what V8 is doing.

I have tried this in v0.11.14 (V8 version 3.26.33 vs 3.14.x in v0.10.x) and it seems that the problem is gone.

Unfortunately, I don't think there's much that can be done about, unless you plan on changing some of the V8 inner workings.

[trevnorris]

Yes. This is a V8 issue and not much we can do in Node.