On Demand Javascript Loading (with XMLHttp)

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Generally, when you want to link a javascript file in one of your HTML pages, you would do something like the following:

<script type = "text/javascript" src = "./myfile.js"></script>

This is fine in many cases, but what happens if you want to give your users the ability to customize the web page? Suppose you want your users to be able to add widgets and the logic for each of those widgets is cleanly separated into individual files? One option might be to simply include every javascript widget file that the user might want to invoke. But that's going to increase page bloat when (in many cases) it isn't necessary. Wouldn't it be better if we waited until the user requested a widget and then dynamically loaded the necessary javascript to create that widget?

Through some innovative use of XMLHttp, we can achieve exactly this. Read on to find out how.

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