Using ReqiureJS to have local instances of 3rd party libraries

Question

My application's JavaScript uses jQuery and jQuery plugins and running in "hostile" environment I have no control over (this is PHP extension for eCommerce platform). Thus no way to determine whether my jQuery code will be executed before someone will attach his instance of jQuery/plugins (introduced by other extension) or after this or someone will load jQuery dynamically after page rendered.

Basically the problem is that other extension could use jQuery (with plugins) also and just connecting jQuery with tag will not work.

I have a strong feeling that RequireJS might help me to load needed version of jQuery as far as particular versions of jQuery plugins into the encapsulated scope without polluting global scope (so other extensions will still function properly). Then I'll wrap all my code to "require" statements and it will run using it's own set of jQuery and plugins. I tried this and it kind of works (have not tested this in production environment though) but in some weird way. Seems like this question is kind of relevant to problems I have. Also answer suggesting to use AMD-compatible version of jQuery. But what about plugins? I don't think all plugins I use have such versions.

So questions:

Could RequireJS be used to cover such use case (running jQuery+plugins in undefined environment)? If RequireJS could be used there then any example code or explanation of how to do this properly will be greatly appreciated. If there is no way to cover this with RequireJS what do you think would be best approach to handle issue?

Answer 1

Yes, I believe RequireJS can help you out here. To my knowledge you'll have to do some legwork, though. Take a look at the source of the (as of 2012-08-19) latest jQuery: link . At the bottom you can see that window.jQuery is being set, defining jQuery and $ . The define call for AMD loaders happens after that, so jQuery is in the global scope no matter what. What you want to do is guarantee that your own version of jQuery and plugins stay isolated from other jQuery instances and plugins, correct?

Place your custom jQuery and plugins into their own directory (let's call it "jqcustom") and use that directory when specifying dependencies in your scripts' define calls. You'll want to modify your version of jQuery by wrapping it in a define call and returning the jQuery object at the very bottom, taking out jQuery's window.jQuery and window.$ assignments as well as its default define call in the process (these are both at the bottom, remember). Then you'll need to wrap all of your plugins in define calls and specify your own version of jQuery as the dependency. Example:

define(['jqcustom/jquery'], function(jQuery) {
    //inside this method 'jQuery' will override any predefined global window.jQuery

    //in case any plugins use the $ variable, define that locally too
    var $ = jQuery;

    //... plugin code ...

});

If you use RequireJS' optimizer, it can do the wrapping of the plugins for you with its shim config options. jQuery plugins work by adding methods to jQuery's prototype object, so I believe as long as you pass the same jQuery (your custom jqcustom/jquery one) to every plugin with your define wrapping, the plugins' extensions will all be set on the same object and be accessible in subsequent define calls specifying your custom jQuery or custom plugins as dependencies. Good luck!