What does window.jQuery and window.$ mean?

Question

Are they native properties of window if so why is it called jQuery, surely jquery came after javascript

Edit: I was looking through jquery.js and found these two lines which made me wonder about what they mean exactly. If wouldn't window.Jquery be null since JQuery is not a variable of window?

_jQuery = window.jQuery,

_$ = window.$,

Answer 1

I will pull from an article I linked to in a comment above:

As discussed in the JavaScript Basics section, valid names in JavaScript can be pretty much anything, as long as they don't begin with a number and don't include a hyphen. So, the $ in the code above is just a shorter, more convenient name for the jQuery function; indeed, in the jQuery source code, you'll find this near the end:

// Expose jQuery to the global object
window.jQuery = window.$ = jQuery;

When you call the $() function and pass a selector to it, you create a new jQuery object. Of course, in JavaScript, functions are objects too, so that means that $ (and jQuery, of course) has properties and methods, too. For example, you can refer to the $.support property for information on what the current browser environment supports, and you use the $.ajax method to make an AJAX request.

Basically, jQuery (when you include it) creates functions at window.$ and window.jquery. Then it sets $ equal to both of those to $ for convenience.