CODEWITHSUNDEEP
jquery
Muaz Khan
Muaz Khan

Reputation: 7236

Using javascript to check which CDN jQuery is cached from on the client

Can I use JavaScript to check whether JQuery is (already) downloaded (cached) on the target web browser (user) or not? For Example:

If (JQuery-from-Microsoft-CDN-downloaded)
    Then use http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.4.4.js
Else if (JQuery-from-Google-APIs- downloaded)
    Then use http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js
Else if (JQuery-from-code.jquery.com- downloaded)
    Then use http://code.jquery.com/jquery-1.4.4.min.js
Else use jQuery from my own website.

Means that using the ability of javascript to check whether one of them is downloaded on the target User (Web Browser), if not then use jQuery from my own website otherwise if true then use that version of JQuery that is downloaded on the target User.

Upvotes: 5

Views: 673

Answers (2)

Nazariy
Nazariy

Reputation: 6088

There are few ways to check if jQuery is loaded

var isLoaded = (jQuery) ? true : false;

or

var isLoaded = (typeof jQuery == 'undefined') ? false : true;

If your script is loaded inside same document that jQuery included you can parse DOM and check if any of the SCRIPT tag containing link to any of the CDN's

var jQueryVersion = isLoaded ? jQuery.fn.jquery : false;

Upvotes: 0

Nick Craver
Nick Craver

Reputation: 630489

You can't do this, another case where the same-origin policy prevents any mechanism to accomplish this. If you think about it, it makes sense...any mechanism you could use to accomplish this, you could also use to figure out which sites someone visited, by seeing which files they have cached.

Upvotes: 4

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