There have been occasions where I have desired to retrieve the HTML of pages other than the one I am typically on. This has happened either when I am using a browser's JavaScript console or when I am writing a bookmarklet. So, given any URL, I wish to retrieve the content of that URL so that I may then use it in, say, a JavaScript variable.
The desired solution cannot use jQuery since that requires loading an external library, which is only optimal in the context of JavaScript that is running in a webpage (as opposed to a console or from a bookmarklet). (Also, adding a script tag to a page just to use in the console is clunky.)