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copied!<p>You can also use instanceof, example with basic polymorphism.</p> <p>First create a superclass (ball)</p> <pre><code>// superclass function Ball() { this.play = function() { alert("Ball throw"); }; } </code></pre> <p>and now for some subclasses (types of balls)</p> <pre><code>// subclass function Basketball() { this.play = function() { alert("basketball throw"); }; } // subclass function Soccerball() { this.play = function() { alert("soccer ball kick/throw"); console.debug("here"); }; } // subclass function Baseball() { this.play = function() { alert("strike 3 you're out"); console.debug("here"); }; } </code></pre> <p>Give them Ball functionality, aka set their superclass via prototype</p> <pre><code>// set subclass functionality Basketball.prototype = new Ball(); Soccerball.prototype = new Ball(); Baseball.prototype = new Ball(); </code></pre> <p>Some polymorphism (create a bunch of balls and play with them all, but play based on type)</p> <pre><code>var bunchOfBalls = [new Baseball(), new Soccerball(), new Basketball()]; for (var i = 0; i < bunchOfBalls.length; i++) { bunchOfBalls[i].play(); } </code></pre> <p>Now write a function that takes a ball but only want to to work for specific type of balls (mimic function overloading, more or less)</p> <pre><code>//overloading dependent upon type function BasketbalOrBaseballOnlyPlay(aBall) { if (aBall instanceof Basketball) { //special basketball function } if (aBall instanceof Baseball) { //special baseball function } } </code></pre> <p>If aBall is a Basketball so <code>aBall = new Basketball();</code> then <code>aBall instanceof Basketball</code> would return true for Basketball and false for baseball but true for Ball.</p> <p>So <code>aBall instanceof Ball</code> would return true because a Basketball is a Ball. </p> <p><a href="http://jsfiddle.net/kLCPB/" rel="nofollow">See code live at <a href="http://jsfiddle.net/kLCPB/" rel="nofollow">http://jsfiddle.net/kLCPB/</a></a></p>

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