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copied!<p>You are confusing the <code>prototype</code> property that can be used on <a href="https://developer.mozilla.org/En/Core_JavaScript_1.5_Guide/Creating_New_Objects/Using_a_Constructor_Function" rel="noreferrer">Constructor Functions</a> and the <em>internal</em> <code>[[Prototype]]</code> property.</p> <p>All objects have this internal <code>[[Prototype]]</code> property, and only the <a href="http://bclary.com/2004/11/07/#a-11.2.2" rel="noreferrer"><code>new</code></a> operator when you call it with a constructor function is allowed to set it (through the <a href="http://bclary.com/2004/11/07/#a-13.2.2" rel="noreferrer"><code>[[Construct]]</code></a> internal operation).</p> <p>If you want to have prototypal inheritance with object instances (without using constructors), the Crockford's <a href="http://javascript.crockford.com/prototypal.html" rel="noreferrer"><code>Object.create</code></a> technique is what you want (that method is now part of the recently approved ECMAScript 5th Edition):</p> <pre><code>// Check if native implementation available if (typeof Object.create !== 'function') { Object.create = function (o) { function F() {} // empty constructor F.prototype = o; // set base object as prototype return new F(); // return empty object with right [[Prototype]] }; } var confProto = { d: 16 }; var conf = Object.create(confProto); conf.a = 2; conf.b = 4; </code></pre> <p>In the above code <code>conf</code> will have its three members, but only <code>a</code> and <code>b</code> will exists physically on it:</p> <pre><code>conf.hasOwnProperty('a'); // true conf.hasOwnProperty('b'); // true conf.hasOwnProperty('d'); // false </code></pre> <p>Because <code>d</code> exists on the conf <code>[[Prototype]]</code> (<code>confProto</code>).</p> <p>The <a href="http://bclary.com/2004/11/07/#a-11.2.1" rel="noreferrer">property accessors</a>, <code>.</code> and <code>[]</code> are responsible to resolve the properties looking up if necessary in the prototype chain (through the <a href="http://bclary.com/2004/11/07/#a-8.6.2.1" rel="noreferrer"><code>[[Get]]</code></a> internal method).</p>

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