$ Variable (Dollar Sign) in Chrome?

Question

I was working with the developer tools of google chrome on a page without jQuery (or any other library that uses the $ sign as a shortcut). When I inspected $ by the console (by just typing it in and hitting enter), i got this:

$
function () { [native code] }

So, chrome has some native function that can be referenced by $. Only chrome seems to have this one and i cannot access it via window['$'] nor via document['$'] or this['$'].

I was not able to find out what this function is. Do you know what it does and maybe have some background information on this? Thanks in advance!

Answer 1

This has changed yet again, even since just last year.

The devtools console provides $ as an alias to document.querySelector, along with many other things; here's an excerpted list:

• $(selector) returns the reference to the first DOM element with the specified CSS selector. This function is an alias for the document.querySelector() function.
• $$(selector) returns an array of elements that match the given CSS selector. This command is equivalent to calling document.querySelectorAll().
• $_ returns the value of the most recently evaluated expression.
• The $0, $1, $2, $3 and $4 commands work as a historical reference to the last five DOM elements inspected within the Elements panel or the last five JavaScript heap objects selected in the Profiles panel.

...and a bunch of others.

Note how it calls $ an alias of document.querySelector, but says $$ is "equivalent" to calling document.querySelectorAll. Neither seems to be literally true; $ === document.querySelector is false, and $$ returns an array, not a NodeList.

Answer 2

Ther're two selectors in Webkit inspectors, the same that Mootools one : $ and $$

You can find some informations on it, here

They're juste here to help you in debug.

Answer 3

It is one of the Chrome Developer Tools functions (so not available from the page). You can see documentation for it on the Console page.

It gets an element by a selector.

Firefox implements something similar

Answer 4

https://developers.google.com/chrome-developer-tools/docs/console

It's just quick access to document.getElementById.

Answer 5

Judging by the link to the dev tools it is now uses document.querySelector() rather than just getElementById().

Answer 6

The existing answers are outdated, $ is not an alias for document.getElementById or document.querySelector, but a wrapper for querySelector. This wrapper actually takes an optional second argument for the element to query the child of.

For Chrome this family of functions is documented under the Console Utilities API reference:

$(selector [, startNode])

$(selector) returns the reference to the first DOM element with the specified CSS selector. When called with one argument, this function is a shortcut for the document.querySelector() function.

$$(selector [, startNode])

$$(selector) returns an array of elements that match the given CSS selector. This command is equivalent to calling Array.from(document.querySelectorAll()).

$x(path [, startNode])

$x(path) returns an array of DOM elements that match the given XPath expression.

Firefox also documents their implementation of these functions under Web Console Helpers (currently the same except $x allows a 3rd argument).

I don't know if/where Safari/WebKit documents it, but it also implements them the same as Chrome.

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Note that these values are only the default values within the console versus the page itself. For example if the page sets the variable by including jQuery that variable will take precedent and the console will use the value from the page itself so that $('p') will return a jQuery object rather than just the first p element.