Checking a jquery plugin exists before using it

David Jones

When creating a simple static website we all know there often isn’t the need to include all the javascript libraries you have on every page. For example i often use fancybox for some nice popups of google maps etc so i will only need to include the fancybox jquery plugin on the contact us page and maybe a gallery page if i happen to use it there too. This works great but because i also keep my javascript which enables the plugins in a seperate file called common.js i run into a problem where i will get a few errors on the other pages saying it didn’t understand the property or function fancybox() because i didn’t include the library on those pages. Sometimes this error can then prevent further javascript from executing and cause all kinds of problems you may be unaware of. A simple solution is to use a little check like this to make sure you have a plugin loaded or not.

         // jquery fancybox is there now we can use it!
} else {
         // jquery fancybox hasn't been loaded

In this example i have just used fancybox but you should be able to use this in any other plugin such as the nivo slider etc. This has become a common practice for me now just as i would use isset in php i now use this in javascript.


  • avatar-hups
    # hups

    hello how can i load all fancybox.js with mousscroll and easing.

    sorry for bad english .

    i will chek my website if fancybox already been loadet

    for examble i have jquery load

    var jQueryScriptOutputted = false; function initJQuery() {

    //if the jQuery object isn't available
     if (typeof(jQuery) == 'undefined') {
         if (! jQueryScriptOutputted) {
            //only output the script once..
            jQueryScriptOutputted =  true;
            //output the script (load it from google api)
        setTimeout("initJQuery()", 50);
    }  else {
        $(function() {  
            //do anything that needs to be done on document.ready



    an this for fancybox that was great.

    can you help me ??

  • avatar-davidejones
    # davidejones

    hmm well for a more advanced loading/checking you might want to try using a javascript library like modernizr or yepnope (which is part of the modernizr)

    You can load a js file and set conditions when it couldn’t load it etc

  • avatar-hups
    # hups

    ok i have found it

    if (typeof $.fancybox == ‘function’) { //alert(‘fancybox has been already loaded so there is nothing left todo’); }else {

    //alert(‘I detected nada so I will load the fancybox js file ‘+pfad); document.write('');



    document.write(''); }

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