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I am creating a complete ajax application where there is one base page and any pages the user navigates to within the application are loaded via ajax into a content div on the page. On the base page I include the various scripts that are needed for every page within the application (jQuery, jQuery-UI, other custom javascript files). Then on the various pages with the application I include a script or two for each page that contains the logic needed for just that page. Each of those script files have something that executes on the page ready event. The problem is that every time the user navigates to page1, the page1.js file is loaded. So, if they visit that page 10 times, that script is then loaded ten times into their browser. Looking at the Chrome script developer tools after running around the site I see tons of duplicated scripts.

I read somewhere about checking to see if the script has already been loaded using a boolean value or storing the loaded scripts in an array. But, the problem with that is that if I see the script is already loaded and I don't load it, the page ready function doesn't get fired for the page's javascript file and everything fails.

Is there an issue having the javascript file loaded over and over when the user visit the same page multiple times?

I did notice looking at the network traffic that every time we visit the page, the script is requested with a random number parameter (/Scripts/Page1.js?_=298384892398) which causes the forced request for the script file every time. I set the cache: true settings on the jQuery ajaxSetup method and that removed the parameter from the request and thus the cached version of the javascript file was loaded instead of actually making a separate HTTP request for it. But, the problem is that I don't want all the ajax requests made to be cached as content changes all the time. Is there a way to force just javascript files to be cachced but allow all other ajax requests to be not cached.

Even when I forced caching on all requests, the javascript file still showed up multiple times in the developer tools. Maybe that isn't a big deal but it doesn't seem quite right.

Any advice on how to handle this situation?

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    About your first question:

    Every time you load a JavaScript file, the entire content gets evaluated by the browser. It solely depends on the content if you can load and execute it multiple times in a row. I'd not consider it a best practice to do so. ;)

    Still i'd recommend that you find a way to check if it was already loaded and fire the "page loaded" event manually within the already present code.

    For the second question: I'd assume that the script is intended to show up multiple times when including it multiple times. To give an advice on how to not cache the loaded JS i'd need to know how you loaded the code, how you do AJAX and the general jQuery setup.

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    • Thanks for the advice but check out my answer. Turns out is a Chrome thing.
      – Nick Olsen
      CommentedFeb 17, 2012 at 19:12
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    After doing some more research it looks like it is actually just a Chrome issue. When you load a script via AJAX you can include the following in your code to get it to show up in the the Chrome developer tools

    //@ sourceURL=some-script-name

    The problem is that when you navigate away from the page, the developer tools keeps the script around, but it is actually not longer referenced by the page.

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