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    <p>JavaScript is an OOP language based on prototypes and not classes. That is one of the cause of all this confusion you can see around: a lot of developers use JS as it was a class-based.</p> <p>Therefore, you can see a lot of libraries that trying to use paradigm of a class-based language in JS.</p> <p>In addition, JS itself is lacking of some traits that makes inheritance, also prototype-based, painful. For example, before <code>Object.create</code> there wasn't a way to create an object from another object (as a OOP prototype-based language should do), but only using a <code>function</code> as constructor.</p> <p>And also for that reason, you can see a lot of libraries that are trying to "fix" the language, every one in its own way.</p> <p>So, your confusion is normal. Say that, the "official" way is use <code>prototype</code> property, <code>function</code>s as constructor, and <code>Object.create</code> to create from object's insteance. However, as said above, in some cases the code is verbose or it lacks of functionality, so this procedure is often wrapped somehow, and then it becomes a matter of personal taste.</p> <p>Because you're talking about model, you can take a look to <a href="http://backbonejs.org/#Model-extend">Backbone's Model</a> and see if this approach fits you.</p> <p><strong>Update</strong>: to give some example that I hope helps you to clarify, here the old school inheritance way using <code>new</code>:</p> <pre><code>function Model() { this.foo = "foo"; this.array = []; } Model.prototype.foo = ""; Model.prototype.array = null; Model.prototype.doNothing = function() {}; function RestModel() { this.bar = "bar"; } RestModel.prototype = new Model; RestModel.prototype.bar = "" var myModel = new RestModel(); </code></pre> <p>Now, here the issues:</p> <ol> <li>The constructor of <code>Model</code> is called once, only when the <code>RestModel.prototype</code> is set. Therefore, the <code>foo</code> property for every <code>RestModel</code> instance will be "foo". </li> <li>Not only that, but <em>all</em> <code>RestModel</code> instances will share the same instance of the same array in <code>this.array</code> property. If you create an instance of <code>Model</code> directly, you have a new instance of array for each instances.</li> <li><code>myModel.constructor</code> is <code>Model</code> instead of <code>RestModel</code>. That's because we override <code>prototype</code> with a new instance of <code>Model</code>, that contains <code>constructor</code> equals to <code>Model</code>.</li> <li>If you want to have a new instance of <code>RestModel</code> with a lazy call to the constructor, is not possible.</li> </ol> <p>I think there are the main points, of course they're not the only ones. So, how to solve that issues? As I said, a lot of people did already that, and they create library and frameworks also to limit the verbosity. However, to have an idea:</p> <pre><code>function Model() { this.foo = "foo"; this.array = []; } Model.prototype.foo = ""; Model.prototype.array = null; Model.prototype.doNothing = function() {}; function RestModel() { Model.call(this); this.bar = "bar"; } RestModel.prototype = Object.create(Model.prototype); RestModel.prototype.constructor = RestModel; RestModel.prototype.bar = "" var myModel = new RestModel(); // for lazy constructor call var anotherModel = Object.create(RestModel.prototype); RestModel.call(anotherModel); </code></pre> <p>Notice that if you don't want to use <code>prototype</code> or <code>function</code> as constructor, with <code>Object.create</code> you can do that:</p> <pre><code>var Model = { foo: "", array: null, doNothing: function() {} } var RestModel = Object.create(Model); RestModel.bar = ""; var myModel = Object.create(RestModel); // Assuming you have to set some default values initialize(RestModel); </code></pre> <p>Or:</p> <pre><code>var Model = { foo: "", array: null, doNothing: function() {}, init : function () { this.foo = "foo"; this.array = []; }, } var RestModel = Object.create(Model); RestModel.bar = ""; RestModel.init = function () { Model.init.call(this); this.bar = "bar"; } var myModel = Object.create(RestModel); myModel.init(); </code></pre> <p>In that case you mimic basically the constructor. You can also pass a <code>descriptor</code> to <code>Object.create</code> (see the <a href="https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/create">docs</a>) but it becomes more verbose. Most of the people use a sort of <code>extend</code> function or method (as you probably saw in Backbone example).</p> <p>Hope it helps!</p>
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    1. POCorrect javascript inheritance
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    1. COWhich example do you recommend that I use?
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    2. COAll of them are valid, but in a form or in another they will end up to be verbose. You can imaging if `RestModel` has a lot of new properties or methods for instance. That's what I was talking when I said that JS still lacks something. In order to remove verbosity, or you decide to use a 3rd party libraries, or you create a couples of utility functions to do that. I will avoid the pure `new` approach (the first), and just decided for the 2nd or 3rd, it depends if you feel more comfortable to have something that "resemble" a "class" (so the 2nd) or not (3rd).
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