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    <blockquote> <ul> <li>How would binding work for objects?</li> <li>How listening to change in the form might work?</li> </ul> </blockquote> <h2>An abstraction that updates both objects</h2> <p>I suppose there are other techniques, but ultimately I'd have an object that holds reference to a related DOM element, and provides an interface that coordinates updates to its own data and its related element.</p> <p>The <code>.addEventListener()</code> provides a very nice interface for this. You can give it an object that implements the <code>eventListener</code> interface, and it'll invoke its handlers with that object as the <code>this</code> value.</p> <p>This gives you automatic access to both the element and its related data.</p> <h2>Defining your object</h2> <p>Prototypal inheritance is a nice way to implement this, though not required of course. First you'd create a constructor that receives your element and some initial data.</p> <pre><code>function MyCtor(element, data) { this.data = data; this.element = element; element.value = data; element.addEventListener("change", this, false); } </code></pre> <p>So here the constructor stores the element and data on properties of the new object. It also binds a <code>change</code> event to the given <code>element</code>. The interesting thing is that it passes the new object instead of a function as the second argument. <em>But this alone won't work.</em> </p> <h2>Implementing the <code>eventListener</code> interface</h2> <p>To make this work, your object needs to implement the <code>eventListener</code> interface. All that's needed to accomplish this is to give the object a <code>handleEvent()</code> method. </p> <p>That's where the inheritance comes in.</p> <pre><code>MyCtor.prototype.handleEvent = function(event) { switch (event.type) { case "change": this.change(this.element.value); } }; MyCtor.prototype.change = function(value) { this.data = value; this.element.value = value; }; </code></pre> <p>There are many different ways in which this could be structured, but for your example of coordinating updates, I decided to make the <code>change()</code> method only accept a value, and have the <code>handleEvent</code> pass that value instead of the event object. This way the <code>change()</code> can be invoked without an event as well.</p> <p>So now, when the <code>change</code> event happens, it'll update both the element and the <code>.data</code> property. And the same will happen when you call <code>.change()</code> in your JavaScript program.</p> <h2>Using the code</h2> <p>Now you'd just create the new object, and let it perform updates. Updates in JS code will appear on the input, and change events on the input will be visible to the JS code.</p> <pre><code>var obj = new MyCtor(document.getElementById("foo"), "20"); // simulate some JS based changes. var i = 0; setInterval(function() { obj.change(parseInt(obj.element.value) + ++i); }, 3000); </code></pre> <p><strong><em>DEMO:</em></strong> <a href="http://jsfiddle.net/RkTMD/">http://jsfiddle.net/RkTMD/</a></p>
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    1. POHow to Implement DOM Data Binding in JavaScript
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    1. USSagiruddin Mondal
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    1. CO+1 Very clean approach, very simply put and simple enough for people to learn from, a lot cleaner than what I had. A common use case is using templates in code to represent objects' views. I was wondering how this might work here? In engines like Mustache I do something `Mustache.render(template,object)`, assuming I want to keep an object synced with the template (not specific to Mustache) , how would I go on about that?
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      1. USBenjamin Gruenbaum
    2. CO@BenjaminGruenbaum: I haven't used client-side templates, but I would imagine that Mustache has some syntax for identifying insertion points, and that that syntax includes a label. So I would think that the "static" parts of the template would be rendered into chunks of HTML stored in an Array, and the dynamic parts would go between those chunks. Then the labels on the insertion points would be used as object properties. Then if some `input` is to update one of those points, there would be a mapping from the input to that point. I'll see if I can come up with a quick example.
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    3. CO@BenjaminGruenbaum: Hmmm... I haven't thought about how to cleanly coordinate two different elements. This is a little more involved than I thought at first. I'm curious though, so I may need to work on this a little later. :)
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