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POWhy is my JavaScript function sometimes "not defined"?
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copied!<p>I call my JavaScript function. Why do I <em>sometimes</em> get the error 'myFunction is not defined' when it <em>is</em> defined?</p> <p>For example. I'll occasionally get 'copyArray is not defined' even in this example:</p> <pre><code>function copyArray( pa ) { var la = []; for (var i=0; i < pa.length; i++) la.push( pa[i] ); return la; } Function.prototype.bind = function( po ) { var __method = this; var __args = []; // Sometimes errors -- in practice I inline the function as a workaround. __args = copyArray( arguments ); return function() { /* bind logic omitted for brevity */ } } </code></pre> <p>As you can see, copyArray is defined <em>right there</em>, so this can't be about the order in which script files load.</p> <p>I've been getting this in situations that are harder to work around, where the calling function is located in another file that <em>should</em> be loaded after the called function. But this was the simplest case I could present, and appears to be the same problem.</p> <p>It doesn't happen 100% of the time, so I do suspect some kind of load-timing-related problem. But I have no idea what.</p> <p>@Hojou: That's part of the problem. The function in which I'm now getting this error is itself my addLoadEvent, which is basically a standard version of the common library function.</p> <p>@James: I understand that, and there is no syntax error in the function. When that is the case, the syntax error is reported as well. In this case, I am getting only the 'not defined' error.</p> <p>@David: The script in this case resides in an external file that is referenced using the normal <script src="file.js"></script> method in the page's head section.</p> <p>@Douglas: Interesting idea, but if this were the case, how could we <em>ever</em> call a user-defined function with confidence? In any event, I tried this and it didn't work.</p> <p>@sk: This technique has been tested across browsers and is basically copied from the <a href="http://en.wikipedia.org/wiki/Prototype_JavaScript_Framework" rel="noreferrer">Prototype</a> library.</p>

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