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POJavascript equivalent to C#s "protected"
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copied!<p>The code below uses Javascript to create a base class, <code>eventRaiser</code>, that has the internals needed to allow clients to subscribe to events, <strong>and subclasses</strong> to raise these events. The idea is that other classes, like <code>ThingWithEvent</code>, will inherit from <code>eventRaiser</code> and expose the subscribe method, and fire off the raise method internally. The jQuery init function demonstrates this.</p> <p>The way this is written, there's nothing stopping a client from directly raising an event. In other words, adding <code>er.raise("Y");</code> to the jQuery init function causes the Y event to be raised without difficulty. </p> <p>Ideally I'd like to make it so that outside code, interacting with <code>eventRaiser</code> through some class that inherits from it, with can only subscribe to events, and not raise them. </p> <p><strong>In other words I'd like <code>raise</code> to be the equivalent of C# <code>protected</code>—visible only to itself, and classes that inherit from it.</strong></p> <p>Is there some slick ninja closure I should use to achieve this, or should I recognize that Javascript is not meant to incorporate OO Encapulation, rename <code>raise</code> to <code>_raise</code> to imply to client code that <code>_raise</code> is private and should not be invoked, and move on?</p> <pre><code> $(function() { var er = new ThingWithEvent(); er.subscribe("X", function() { alert("Hello"); }); er.subscribe("X", function() { alert("World"); }); er.subscribe("Y", function() { alert("Not Called"); }); er.doSomething("X"); }); function eventRaiser() { var events = {}; this.subscribe = function(key, func) { if (!events[key]) events[key] = { name: key, funcs: [] }; events[key].funcs.push(func); }; this.raise = function(key) { if (!events[key]) return; for (var i = 0; i < events[key].funcs.length; i++) events[key].funcs[i](); }; } function ThingWithEvent() { eventRaiser.call(this); var self = this; this.doSomething = function() { alert("doing something"); self.raise("X"); } } function surrogate() { } surrogate.prototype = eventRaiser; ThingWithEvent.prototype = new surrogate(); ThingWithEvent.prototype.constructor = ThingWithEvent; </code></pre>

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