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POCan I construct a JavaScript object without using the new keyword?
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copied!<p>Here is what I'd like to do:</p> <pre><code>function a() { // ... } function b() { // Some magic, return a new object. } var c = b(); c instanceof b // -> true c instanceof a // -> true b instanceof a // -> true </code></pre> <p>Is it possible? I can make <code>b</code> be an instance of <code>a</code> easily by hooking <code>a</code> into its prototype chain but then I have to do <code>new b()</code>, which is what I'm trying to avoid. Is what I want possible?</p> <p><strong>Update:</strong> I feel that it might be possible with judicious use of <code>b.__proto__ = a.prototype</code>. I'm going to experiment more after work.</p> <p><strong>Update 2:</strong> Below is what seems to be the closest you can get, which is good enough for me. Thanks all for the interesting answers.</p> <pre><code>function a() { // ... } function b() { if (!(this instanceof arguments.callee)) { return new arguments.callee(); } } b.__proto__ = a.prototype var c = b(); c instanceof b // -> true c instanceof a // -> false b instanceof a // -> true </code></pre> <p><strong>Update 3:</strong> I found exactly what I wanted in a <a href="http://blog.higher-order.net/2008/02/21/javascript-parasitic-inheritance-power-constructors-and-instanceof/" rel="noreferrer">blog post on 'power constructors'</a>, once I added the essential <code>b.__proto__ = a.prototype</code> line:</p> <pre><code>var object = (function() { function F() {} return function(o) { F.prototype = o; return new F(); }; })(); function a(proto) { var p = object(proto || a.prototype); return p; } function b(proto) { var g = object(a(proto || b.prototype)); return g; } b.prototype = object(a.prototype); b.__proto__ = a.prototype; var c = b(); c instanceof b // -> true c instanceof a // -> true b instanceof a // -> true a() instanceof a // -> true </code></pre>

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