Comments on: Implementing an Array.count() Method in JavaScript

By: Patrick

Patrick — Thu, 03 Nov 2011 15:03:09 +0000

I think it’s okay for personal project but it has a counter side when you are in enterprise. The maintainability is harder when people use custom extension (prototype existing framework object). It cane be confusing. In some case, I have seen people creating function to simply get an object inside an array. I think this should be used with parsimony. But, it’s just my opinion…

By: Everwebby

Everwebby — Tue, 04 Oct 2011 13:49:19 +0000

Riv, thats a much better form of the count use. Its surprising that this is not built into javascript.

By: Christian

Christian — Tue, 27 Sep 2011 16:43:11 +0000

Array.prototype.count = function () {
for (k in this) { if (this[k].constructor !== Function) { this.length++; } };
return this.length;
}

By: riv

riv — Fri, 03 Apr 2009 01:30:48 +0000

That’s right and that’s what I was expecting when searching for count on js. This should do it:

function count(array)
{
var c = 0;
for(i in array) // in returns key, not object
if(array[i] != undefined)
c++;

return c;

}

By: Jason

Jason — Sun, 19 Oct 2008 17:27:16 +0000

Correction to my previous post:

the second code snippet would be:

var myOtherArray = [];
myOtherArray[100] = ‘one’;

and its length property would actually return 101.

By: Jason

Jason — Sun, 19 Oct 2008 17:23:38 +0000

This is all fine and well, but length is fundamentally different from count.

Take the following example:

var myArray = ['one', 'two', 'three'];
// myArray.length == 3, as we would expect

var myOtherArray[100] = ‘one’;
//myArray.length == 100, NOT 1

Even though we only have 1 item in the array, ‘length’ refers to the largest index + 1. Unlike PHP where we can use numeric keys and strings for indexes in an ad hoc way and still get an accurate count via count(), in JS it’s not quite the same.

In a way, this is just splitting hairs, but a lot of people already don’t understand JS’s length property, and referring to it as “count” only serves to further the confusion.

By: david

david — Thu, 26 Jun 2008 03:33:03 +0000

@Binny: No, I don’t. Just arrays.

By: Binny V A

Binny V A — Wed, 25 Jun 2008 17:32:21 +0000

Do you do this for strings as well?

By: Rich

Rich — Wed, 25 Jun 2008 14:27:16 +0000

Thanks for your blog. you offer great advice and tutorials and for some odd reason, if I am looking to see how to complete a task, you have a tutorial on it or at least an idea on the concept I am trying to achieve; so thanks David. Although this post came about 2 days too late. :)