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POJavaScript singleton pattern and 'this'
 

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  1. POJavaScript singleton pattern and 'this'
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    <p>After reading a lot of articles on singleton pattern, and making some tests, I found no difference between the singleton pattern like this (<a href="http://jsfiddle.net/bhsQC/1/" rel="nofollow">http://jsfiddle.net/bhsQC/1/</a>):</p> <pre><code>var TheObject = function () { var instance; function init() { var that = this; var foo = 1; function consoleIt() { console.log(that, foo); } return { bar: function () { consoleIt() } }; } return { getInstance: function () { if (!instance) { instance = init(); } return instance; } }; }(); var myObject = TheObject.getInstance(); myObject.bar(); </code></pre> <p>and code like this (<a href="http://jsfiddle.net/9Qa9H/3/" rel="nofollow">http://jsfiddle.net/9Qa9H/3/</a>):</p> <pre><code>var myObject = function () { var that = this; var foo = 1; function consoleIt() { console.log(that, foo); } return { bar: function () { consoleIt(); } }; }(); myObject.bar(); </code></pre> <p>They both make only one instance of the object, they both can have "private" members, <code>that</code> points to <code>window</code> object in either of them. It's just that the latter one is simpler. Please, correct me if I'm wrong.</p> <p>Using standard constructor like this (<a href="http://jsfiddle.net/vnpR7/2/" rel="nofollow">http://jsfiddle.net/vnpR7/2/</a>):</p> <pre><code>var TheObject = function () { var that = this; var foo = 1; function consoleIt() { console.log(that, foo); } return { bar: function () { consoleIt(); } }; }; var myObject = new TheObject(); myObject.bar(); </code></pre> <p>has the advantage of correct usage of <code>that</code>, but isn't a singleton.</p> <p>My question is: <strong>what are the overall advantages and disadvantages of these three approaches?</strong> (If it matters, I'm working on a web app using Dojo 1.9, so either way, this object will be inside Dojo's <code>require</code>).</p>
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    1. COJust out of the curiosity why would someone use the singleton pattern in JavaScript? Wouldn't it make sense to use one object like: var obj1 = { } Sorry for offtopic
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      1. USKir Ivlev
    2. CO@KirillIvlev with singleton/module pattern you can have private vars and functions inside the IIFE. The singleton from OP seems to apply lazy loading as well - only instantiate when first called.
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      1. USFabrício Matté
    3. COI'd rather simply use an auto-invoking function to hide away the constructor, i.e., something like this: http://jsfiddle.net/qFMcL/
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