Which javascript object creation is more efficient?

Question

I understand the recommended manner is Version 2 (below), using prototype. However, what is the difference between the two versions because not only does Version 1 sometimes beat Version 2 in memory consumption, it also routinely completes in half to a third of the time (according to my tests using Chrome).

Version 1:

   var C = function() { console.log("new C"); }

   C.f = function(foo) { console.log("function"); }

   var a = [];
   for (var i = 0; i < 100000; i++) {
       a.push(new C());
   }

Version 2:

   var C = function() { console.log("new C"); }

   C.prototype.f = function(foo) { console.log("function"); }

   var a = [];
   for (var i = 0; i < 100000; i++) {
       a.push(new C());
   }

possible duplicate of Closures in auto executing functions vs objects — Naftali
– Naftali, Commented Jun 4, 2012 at 19:32
Are you "extending" the object? Or simply creating the object to be used? — mawcsco
– mawcsco, Commented Jun 4, 2012 at 19:32
Your scripts are not equivalent. In the first case, f is a property of the constructor function C, that means the instances you create with new C() do not have a reference to f. In the second one, you assign f to C's prototype, from which all instances inherit. You are comparing apples with oranges. It should not make a difference in the performance though... here is a jsPerf testcase: jsperf.com/static-vs-prototype — Felix Kling
– Felix Kling, Commented Jun 4, 2012 at 19:32
@FelixKling: But shouldn't both scripts should run in the same time and memory? Objects in version 1 should still reference C.prototype in the same way as version 2 (and I don't know of any clever tricks to get around it here) — hugomg
– hugomg, Commented Jun 4, 2012 at 19:37

Sebas · Accepted Answer · 2012-06-04 19:43:54Z

1

version 1 will give the function to your object only, while version 2 will provide the function to all object from the function holding the prototype.

And actually I'm pretty curious to see if any of your new C(); instanciations in version 1 has access to the C.f method...

edited Jun 4, 2012 at 19:43

answered Jun 4, 2012 at 19:33

Sebas

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1 Comment

Felix Kling Over a year ago

Theoretically yes, through instance.constructor.f (my comment was actually not precise enough), but I don't think that this is the desired way ;)

Guffa · Accepted Answer · 2012-06-04 19:58:17Z

0

Any performance difference is moot, because the first version doesn't work.

Adding a function as a property to a constructor function doesn't make it a method in the created object.

answered Jun 4, 2012 at 19:58

Guffa

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Comments

martsbradley · Accepted Answer · 2012-06-04 20:05:06Z

0

To test out JavaScript language away from the browser you could use my Script Scraper tool.

enter image description here

thanks, Martin.

answered Jun 4, 2012 at 20:05

martsbradley

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