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With $.getScript I can load js files on the fly. Is it possible to "unload" some of these files ?

I have a ajax-based administrative panel. I have 3 sections. When clicking on each section I want to load only the files that are associated with it. When switching to another section I want to unload unnecessary files.

Nick
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5 Answers5

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"Unloading", if it were really possible, wouldn't make much sense here. Let's take a step back and look at why you don't load all the files to begin with:

  • They're another HTTP request and X bytes, if you don't need them, don't get them
  • They have unwanted effects - you don't want what script X does to happen here

Now look at it from the other side, you have loaded them, which means both of the above have already happened, you paid the request cost of getting them and what they've done. Also, what effect they had on the page can't be generically undone. Just by removing a <script> doesn't remove the functions it declared, event handlers it attached, etc.

In short, why are you trying to unload? If it's to remove the effects, well that one's not easy, not in a generic way anyway. If it's to lighten the page...there's no benefit here, you'll actually just incur the cost of removing the element, with no benefit for the client on the JavaScript side of things.

Nick Craver
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  • I use ui autocomplete plugin. From the database I get information and put in the javascript array. This array is passed to ui autocomplete. Array consists of approximately 100 000 elements. I`m worry lest in time to eat a lot of computer memory. – Nick Jan 12 '11 at 13:50
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    @John - Oh in that case you're just looking for [`delete`](https://developer.mozilla.org/en/JavaScript/Reference/Operators/Special/delete), like this: `delete myArray;` to free up the memory. – Nick Craver Jan 12 '11 at 13:55
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    @Nick - what if i would like to run some unit tests, some of them would require me to load aditional html and js scripts from the server, after finishing a batch of tests i would like to remove all the dom elements, objetcs, actions ... AND all the scripts i downloaded for that batch of tests . – Poelinca Dorin Aug 04 '11 at 11:29
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As pointed by Nick Craver it is hard to understand the reason of why you would want to do that.

However if there would be a valid reason to do so. I would put all the code of loaded script in a class. And when i would like to unload this, i would just assign it to null. eg.

//external file:
o1=new Object();
o1.function1=function(){
     //blah blah blah
   };
o1.function2=function(){
     //blah blah blah
   };
o1.var1=1;

//and if when i'll need to get rid of all of this i can just
o1=null;
Ivan
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  • Wouldn't delete o1 be more efficient than setting it to null? – Ed Bayiates Jul 26 '12 at 00:08
  • @AresAvatar delete only works with object properties. So in this case it would work as o1 is appended to window object as a property. But if it was var o1=new Object() it would fail. So assigning to null is a safer option in my opinion, plus it most probably is faster as well. as it is just one simple operation comparing to a function call – Ivan Jul 26 '12 at 15:34
  • Ivan, that is not correct. I can delete "var o1 = {};" and o1 is then undefined. Also, delete isn't a function call. It's a built in operation. Setting to null leaves o1 defined. – Ed Bayiates Jul 26 '12 at 21:38
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    Interesting, I was wrong. The results differ if you are inside a function, and delete seems to have no effect in this case. Thanks for the fiddle! +1 on your solution. – Ed Bayiates Jul 27 '12 at 17:34
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I think that there are valid reasons to load and unload scripts. I have written a monitoring tool where content is swapped in and out of the center <div> all the time. Each load requires new functions to be attached to the just loaded content. If you (un)load js specific to the (un)loaded content, then the memory footprint stays small. And you can re-use previously defined function names for slightly different responses, while writing generic xhtml.

Assume a <div> with info on a peace of data. The user wants to edit that specific record so the <div> content is replaced by a form with all kinds of behaviors on buttons, checkboxes, etc. The form is subitted and the <div> is replaced with the original content but reflecting the changes. The form is gone and so is the need for any associated behavior.

I.m.h.o. loading in a certain <div> on your page x.htm + x.css + x.js and replacing them when other content and behavior is needed is by far preferrable over re-analyzing the new content and attach all possible responses even if certain nodes or classes are missing in the new content.

Instead of large javascript files, a set of pluggable js modules keeps my code well-organized and the maintenance of ajax behaviors relatively easy. Support for such a scheme in jQuery would be a tremendous help (for me).

Erik
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0

You can simply append and remove js files from head:

$('script').last().remove();`//remove last file from html file
$('head').append('<script src=""></script>'); //add js file
Vladi Ivanov
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  • This is also a great solution. Also you can do this more secure with it not showing up in the dom at all if anyone is interested by doing var s = document.createElement("script"); s.type = "text/javascript"; s.src = "http://somedomain.com/somescript"; $("head").append(s); –  Apr 14 '20 at 11:52
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What I would do in this case would be to make all your JavaScript code part of an object structure then simply set the object to null once done with it.

var myObj = {
    "property1": true,
    "property2": "Hello my name is Sam.",
    "mynamedfunction": function(){
       //do stuff
    },
    "othernamedfunction": function(){
       //do other stuff
    }
};

Once done set myObj=null;

So rather than loading and unloading a file you are loading and unloading an object as needed! So you would load the file containing the object in, but then set the object to null once done with it, you can even load it in again after destroying it this way.