Web Inspector and Firefox Dollar Functions

By  on  

Dollar Functions

Many of you probably didn't know this but WebKit-based like Safari and Chrome, in addition to Firefox, contain special dollar functions within the console object that allow you to grab elements within the current page.  While I've not determined the use of each method, a few of them are obvious:

// Dollar method
// Returns an element by ID
$ = function (id) {
	return document.getElementById.apply(document, arguments);
}

// Bling-Bling method
// Returns array of nodes found by QSA
$$ = function(selector) {
	return document.querySelectorAll.apply(document, arguments);
}

// Broke method
// returns the currently selected element within the console HTML pane
$0 = function toString() { [native code] }

The $1 - $4 methods are returning undefined, oddly enough.

Dollar Functions

It's not clear to me what the last few methods do.  Maybe they're placeholders for feature methods but they continue to be undefined for now.

Recent Features

  • By
    Responsive and Infinitely Scalable JS Animations

    Back in late 2012 it was not easy to find open source projects using requestAnimationFrame() - this is the hook that allows Javascript code to synchronize with a web browser's native paint loop. Animations using this method can run at 60 fps and deliver fantastic...

  • By
    Creating Scrolling Parallax Effects with CSS

    Introduction For quite a long time now websites with the so called "parallax" effect have been really popular. In case you have not heard of this effect, it basically includes different layers of images that are moving in different directions or with different speed. This leads to a...

Incredible Demos

  • By
    Font Replacement Using Cufón

    We all know about the big font replacement methods. sIFR's big. Image font replacement has gained some steam. Not too many people know about a great project named Cufón though. Cufón uses a unique blend of a proprietary font generator tool...

  • By
    Create Digg URLs Using PHP

    Digg recently came out with a sweet new feature that allows users to create Tiny Digg URLs which show a Digg banner at the top allowing easy access to vote for the article from the page. While I love visiting Digg every once in a...

Discussion

  1. Brian

    $0 returns whatever you have selected in the Elements tab.

    These all work in Firebug too, by the way.

  2. $0 and $1 return the currently selected DOM element and the previously selected DOM element, respectively. I haven’t yet found a use for this while debugging, mainly because selecting elements in the inspector and debugging in the console seem (for me at least) to be disconnected tasks, but maybe there will be a reason some day? ^_^

    Not sure about webkit’s inspector, but you can find the API for firebug’s CLI here: http://getfirebug.com/wiki/index.php/Command_Line_API

  3. Matthew F

    Perhaps if they plan to use it in the future, they have to reserve it now so that the dom-modifying frameworks don’t start using it :)

  4. Didn’t know about this, the bling-bling method is cool though, haha.

  5. farkob

    Now I get it, this is why Douglas Crockford says you shouldn’t use $ functions.

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!