CODEWITHSUNDEEP
javascriptjquery
Frazer Kirkman
Frazer Kirkman

Reputation: 1154

Does this function execute : jQuery(".class").function(); if the class is not found on this page?

Just a quick question.

I'm wondering if in the following code if unslider() will run if there is no .banner class on the page?

jQuery(".banner").unslider();

I do not want it to run on pages where there is no .banner class.

Do I need to do something like

if (jQuery(".banner") > 0){ jQuery(".banner").unslider(); }

Upvotes: 0

Views: 148

Answers (4)

Ja͢ck
Ja͢ck

Reputation: 173642

Yes, it runs and executes the following (source):

$.fn.unslider = function(o) {
    var len = this.length;

    //  Enable multiple-slider support
    return this.each(function(index) {
        //  Cache a copy of $(this), so it 
        var me = $(this);
        var instance = (new Unslider).init(me, o);

        //  Invoke an Unslider instance
        me.data('unslider' + (len > 1 ? '-' + (index + 1) : ''), instance);
    });
};

So it does a .each() on your collection.

However, if that collection is empty, the function passed to .each() will not run and therefore "not much" would describe best what would happen if you run $('.banner').unslider();

Btw, it wouldn't make sense to try and "optimize" this by doing a .length check unless you're certain that the call will be heavy.

Upvotes: 2

Rajaprabhu Aravindasamy
Rajaprabhu Aravindasamy

Reputation: 67207

Normally the follow up actions wont get executed if the class is not available, but doing a preliminary check will be safer one.

You have to like this,

if(jQuery(".banner").length > 0){ jQuery(".banner").unslider(); }

Or

if(jQuery(".banner").length){ jQuery(".banner").unslider(); }

Upvotes: 0

Adil
Adil

Reputation: 148150

You need to use the length property to check if element exists. 

if (jQuery(".banner").length > 0)
{ 
   jQuery(".banner").unslider(); 
}

You even do not need to check if it is greater then zero.

if (jQuery(".banner").length)
{ 
   jQuery(".banner").unslider(); 
}

Upvotes: 0

Arun P Johny
Arun P Johny

Reputation: 388406

No, it will not get executed if the element is not found.

The plugin method will get called, but since there are no element matching the selector it should not be doing anyting - but it again depends on how the plugin is implemented

Upvotes: 0

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