I'd like to understand the jQuery plugin syntax

Question

The jQuery site lists the basic plugin syntax for jQuery as this:

(function( $ ){    
  $.fn.myPlugin = function() {      
    // there\'s no need to do $(th         


        

Answer 1

The other answers here are great, but there is one important point that hasn't been addressed. You say:

So it's creating a function, that as far as I can tell will never be run, with the parameter of $, which is already defined?

There is no guarantee that the global variable $ is available. By default, jQuery creates two variables in the global scope: $ and jQuery (where the two are aliases for the same object). However, jQuery can also be run in noConflict mode:

When you call jQuery.noConflict(), the global variable $ is set back to whatever it was before the jQuery library was included. This allows jQuery to be used with other Javascript libraries that also use $ as a global variable.

If you wrote a plugin that relied on $ being an alias for jQuery, then your plugin would not work for users running in noConflict mode.

As others have already explained, the code you posted creates an anonymous function that is called immediately. The global variable jQuery is then passed in to this anonymous function, which is safely aliased as the local variable $ within the function.