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POArray Like Objects in Javascript
 

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    <p>I'm wondering how jQuery constructs its array-like object. The key thing I'm trying to work out is how it manages to get the console to interpret it as an array and display it as such. I know it has something to do with the length property, but after playing a bit I can't quite figure it out. </p> <p>I know this has no technical advantage over a normal array like object as in the example below. But I think it's an important semantic element when users are testing and debugging.</p> <p>A normal Array like Object.</p> <pre><code>function foo(){ // Array like objects have a length property and it's properties use integer // based sequential key names, e.g. 0,1,2,3,4,5,6 just like an array. this.length = 1; this[0] = 'hello' } // Just to make sure add the length property to the prototype to match the Array // prototype foo.prototype.length = 0; // Give the Array like object an Array method to test that it works foo.prototype.push = Array.prototype.push // Create an Array like object var bar = new foo; //test it bar.push('world'); console.log(bar); // outputs { 0: 'hello', 1: 'world', length: 2, __proto__: foo } </code></pre> <p>Where as jQuery would output</p> <pre><code>var jQArray = $('div') console.log(jQArray); // outputs [&lt;div&gt;&lt;/div&gt;,&lt;div&gt;&lt;/div&gt;,&lt;div&gt;&lt;/div&gt;,&lt;div&gt;&lt;/div&gt;] </code></pre> <p>If you run </p> <pre><code>console.dir(jQArray) // Outputs { 0: HTMLDivElement, 1: HTMLDivElement, 2: HTMLDivElement, 3: HTMLDivElement, 4: HTMLDivElement, context: HTMLDocument, length: 5, __proto__: Object[0] } </code></pre> <p>The proto of the jQuery object is especially interesting since its the Object and not jQuery.fn.init as would be expected, also the [0] indicates something as this is what you get when you. </p> <pre><code>console.dir([]) // outputs Array[0] as the object name or Array[x] x being the internal length of the // Array </code></pre> <p>I have no idea how jQuery has set it's proto to be Object[0] but my guess is that answer lies somewhere in there. Anyone got any ideas?</p>
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    1. COI'm not sure about this, but couldn't you create your object then set its prototype to Array.prototype? It will then be an array-like object? Or no?
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    2. COwell as far as I know that will make it a normal array. But I also want to avoid that since I don't want to add all the Array methods to my object, in order to avoid confusion. As some Array methods will actually return a new Array, so when a user uses one of those methods all the other methods that where attached to my array like object will be lost.
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