How does jQuery achieve making $ an alias for the jQuery function?

Question

I’m having a little trouble wrapping my head around the $ sign being an alias for the jQuery function, particularly in a plugin. Can you explain how jQuery achieves this ali

Answer 1

It simply declares a variable. See here

jQuery itself is a large self executing function. This means that it declares a function and then runs it. Inside the function it declares the local jQuery object which is a function.

It will then right at the end of it set window.jQuery = window.$ = jQuery

This is setting both window.jQuery and window.$ to the local jQuery object. We can set global variables by making them properties of the window object.

Now both window.jQuery and window.$ both point at jQuery since objects are passed by reference.

var jQuery = (function() {

    var jQuery = function( selector, context ) {
        ...
    };

    ...

    return (window.jQuery = window.$ = jQuery);

}());

it actaully declares jQuery twice for a small efficiency gain since the when looking for the variable it doesn't have to look upwards into an extra outer function.

You can use two assignments like that because (var a = b) === b

As others have mentioned the fact that $ is a legimate variable name and that functions are first class objects, thus we can treat them as objects also helps to make this possible.