$
and $$
will work on any web page (if jQuery is not included also) on Google Chrome, Firefox and Safari browsers where $
returns first element of selector passed.
Here,
$ is document.querySelector
$$ is document.querySelectorAll
They are native functions of Google Chrome and Firefox browsers, you can see $
and $$
definition in Safari as well.
Open Google in any of Google Chrome, Firefox or Safari, and open Developer Tools to check these results... (why Google, because they won't use jQuery or Moo tools)
$('div'); // returns first DIV in DOM
$$('div'); // returns all DIVs in DOM
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