Include jQuery using code

Question

I must include jQuery in a page using code:

if (typeof window.jQuery === "undefined") {
    document.write('<script type="text/javascript" src="http://code.jquery.com/jquery-latest.min.js"><\/script>');
    if (typeof Prototype !== "undefined") {
        document.write('<script>jQuery.noConflict();<\/script>');
    }
}

But then if I try to use jQuery, Firebug logs "jQuery undefined".

jQuery(document).ready(function() {
    //
});

but jquery is correctly loaded

jQuery

Please read [this](http://unixpapa.com/js/dyna.html) and [this](http://stackoverflow.com/questions/802854/why-is-document-write-considered-a-bad-practice) - these days document.write is really mad function, giving you unexpected results — Peter, Sep 01 '12 at 20:10
After... see this jsfiddle http://jsfiddle.net/pampurio97/B7dq2/ — mcont, Sep 01 '12 at 20:10

Musa · Accepted Answer · 2012-09-01T20:20:25.633

3

I would suggest against using document.write, use dom manipulation.

if (typeof window.jQuery === "undefined") {
    var script = document.createElement('script');
    script.onload = function(){
        if (typeof Prototype !== "undefined") {
            jQuery.noConflict();
        }
    }
    script.src = 'http://code.jquery.com/jquery-latest.min.js';
    document.getElementsByTagName('head')[0].appendChild(script);   
}

http://jsfiddle.net/ALCDr/

edited Sep 01 '12 at 20:20

answered Sep 01 '12 at 20:11

Musa

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I just tried and that doesn't work. I think as long he is getting script from external resource he need to use `window.onload` as in Rob answer – Peter Sep 01 '12 at 20:15
@Musa [checked, still not working..](http://codepad.org/iksxQImB). However it's nice that works to OP :) – Peter Sep 01 '12 at 20:32
@PeterSzymkowski the script needs time to load, that's why that's why the check for Prototype is in the onload function – Musa Sep 01 '12 at 20:35

score 1 · Answer 2 · answered Sep 01 '12 at 20:17

1

window.onload = function() {
  jQuery(document).ready(function() {
    alert('!');
  });
}

do the trick.

answered Sep 01 '12 at 20:17

Peter

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score 1 · Answer 3 · answered Sep 01 '12 at 23:59

The way the HTML5 boilerplate does it is the most efficient way.

<script>window.jQuery || document.write('<script src="js/vendor/jquery-1.8.0.min.js"><\/script>')</script>

This will check to see if jQuery has been defined yet (I.e loaded), or (if not) it will load write the script to the page :).

Include jQuery using code

3 Answers3