How can I check if a jQuery plugin is loaded?

Question

Is there any way to check if a particular plugin is available?

Imagine that you are developing a plugin that depends on another plugin being loaded.

For example I want the jQuery Validation plugin to use the dateJS library to check if a given date is valid. What would be the best way to detect, in the jQuery Valdation plugin if the dateJS was available?

Similar Question [How to check jQuery plugin and functions exists?](http://stackoverflow.com/q/5339876/782535) — Madan Sapkota, Apr 25 '13 at 05:24

Eran Galperin · Accepted Answer · 2011-06-21T23:43:26.660

382

Generally speaking, jQuery plugins are namespaces on the jQuery scope. You could run a simple check to see if the namespace exists:

 if(jQuery().pluginName) {
     //run plugin dependent code
 }

dateJs however is not a jQuery plugin. It modifies/extends the javascript date object, and is not added as a jQuery namespace. You could check if the method you need exists, for example:

 if(Date.today) {
      //Use the dateJS today() method
 }

But you might run into problems where the API overlaps the native Date API.

edited Jun 21 '11 at 23:43

answered Dec 30 '08 at 17:36

Eran Galperin

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if(jQuery.fn.pluginName) {...} is another option – Nagyman Jun 16 '10 at 14:55
6

Maybe a little overkill, but `if ($.isFunction(jQuery.fn.pluginName)) { ... }` will also ensure that it's at least a function. – Noyo Sep 03 '13 at 17:46
i have a function that load the script, ` LoadScript (location,namespcae,callBack)` , callback function is warped under an interval, means until the namespace i.e `window.jQuery` is not set the callback will not run, it work fine but now im tring to load a j query plugin and to check that , i need to call jquery select function like `jQuery().pluginName`, but when i pass it my function parameter like `LoadScript("jquery+plugin.js",jquery().plugin)` jquery() dose not exist yet – Hassan Nisar Khan Apr 15 '16 at 15:54

score 110 · Answer 2 · edited Aug 13 '19 at 14:27

110

If we're talking about a proper jQuery plugin (one that extends the fn namespace), then the proper way to detect the plugin would be:

if(typeof $.fn.pluginname !== 'undefined') { ... }

Or because every plugin is pretty much guaranteed to have some value that equates to true, you can use the shorter

if ($.fn.pluginname) { ... }

BTW, the $ and jQuery are interchangable, as the odd-looking wrapper around a plugin demonstrates:

(function($) {
    //
})(jQuery))

the closure

(function($) {
    //
})

is followed immediately by a call to that closure 'passing' jQuery as the parameter

(jQuery)

the $ in the closure is set equal to jQuery

edited Aug 13 '19 at 14:27

Liam

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answered Mar 28 '11 at 21:54

rmirabelle

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I made a function `function isPluginLoaded(plugin) { return !!$.fn[plugin] }` – styfle Aug 09 '12 at 22:57
2

The first example should be `if(typeof $.fn.pluginname != 'undefined')` – dops Sep 30 '14 at 10:35
1

@dops is correct and I have edited the answer accordingly, although I have used a negated triple rather than double equals equality to compare both type and value. – pwdst Dec 10 '14 at 15:34
1

`$` and `jQuery` are not _always_ interchangeable, as jQuery can be (such as in WordPress) loaded in [no-conflict mode](https://api.jquery.com/jquery.noconflict/). This has caused me to _always_ use the shorthand, no-conflict-safe document ready: `jQuery(function($) { // $ is safe in here.... });` or, as you point out, the closure pattern: `(function($) { // $ is safe in here.... })(jQuery);`, depending on my mood / need. (BTW, upvoted, as the check you recommend is the one I prefer) – random_user_name May 24 '18 at 21:12

score 11 · Answer 3 · answered Mar 23 '10 at 10:47

11

To detect jQuery plugins I found more accurate to use the brackets:

if(jQuery().pluginName) {
    //run plugin dependent code
}

answered Mar 23 '10 at 10:47

Suso Guez

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score 8 · Answer 4 · answered May 04 '13 at 18:49

8

for the plugins that doesn't use fn namespace (for example pnotify), this works:

if($.pluginname) {
    alert("plugin loaded");
} else {
    alert("plugin not loaded");
}

This doesn't work:

if($.fn.pluginname)

answered May 04 '13 at 18:49

trante

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Thanks. Another example - Jquery Cookie plugin – ymakux May 02 '14 at 12:49

score 2 · Answer 5 · answered Jun 13 '15 at 18:42

2

Run this in your browser console of choice.

if(jQuery().pluginName){console.log('bonjour');}

If the plugin exists it will print out "bonjour" as a response in your console.

answered Jun 13 '15 at 18:42

Joshua Pekera

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score 2 · Answer 6 · answered Apr 20 '17 at 12:30

2

jQuery has a method to check if something is a function

if ($.isFunction($.fn.dateJS)) {
    //your code using the plugin
}

API reference: https://api.jquery.com/jQuery.isFunction/

answered Apr 20 '17 at 12:30

HasanG

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score 1 · Answer 7 · edited May 23 '17 at 12:26

1

I would strongly recommend that you bundle the DateJS library with your plugin and document the fact that you've done it. Nothing is more frustrating than having to hunt down dependencies.

That said, for legal reasons, you may not always be able to bundle everything. It also never hurts to be cautious and check for the existence of the plugin using Eran Galperin's answer.

edited May 23 '17 at 12:26

Community

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answered Dec 31 '08 at 08:34

Soviut

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score -1 · Answer 8 · answered Dec 30 '08 at 17:35

-1

This sort of approach should work.

var plugin_exists = true;

try {
  // some code that requires that plugin here
} catch(err) {
  plugin_exists = false;
}

answered Dec 30 '08 at 17:35

ceejayoz

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Almost tempted to downvote for catching what you can (and should) easily detect – pwdst Dec 10 '14 at 15:28

How can I check if a jQuery plugin is loaded?

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