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copied!<p>If your library is doing this in places where there are no embedded closures/callbacks that might have their own value of <code>this</code>, then this is just a "practice" or "style" or "convention" that they decided to follow in their methods. There is NO programming reason to always do it.</p> <p>In the specific coding example you have now added to your question, there is no reason I'm aware of other than a common coding style. This code would generate the same result in slightly smaller code:</p> <pre><code>disable: function(silent) { if (this.rendered) { this.el.addCls(this.disabledCls); this.el.dom.disabled = true; this.onDisable(); } this.disabled = true; if (silent !== true) { this.fireEvent('disable', this); } return this; }, </code></pre> <hr> <p>When there is a callback or closure involved, this is often done because there are callbacks used inside the method where they still want a reference to <code>this</code>, but those callbacks will have their own value of <code>this</code> so assigning:</p> <pre><code>var me = this; </code></pre> <p>or more commonly in other code I've seen:</p> <pre><code>var self = this; </code></pre> <p>is a way of retaining access to that object even in a callback that has a different value of <code>this</code>.</p> <p>Here's a generic example:</p> <pre><code>document.getElementById("myButton").onclick = function () { var self = this; // save reference to button object use later setTimeout(function() { // "this" is not set to the button inside this callback function (it's set to window) // but, we can access "self" here self.style.display = "none"; // make button disappear 2 seconds after it was clicked }, 2000); }; </code></pre>

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