String selectors
) Finds the first descendant element of this document that matches the specified group of selectors.
Unless your webpage contains multiple documents, the top-level querySelector method behaves the same as this method, so you should use it instead to save typing a few characters.
selectors
should be a string using CSS selector syntax.
var element1 = document.querySelector('.className');
var element2 = document.querySelector('#id');
For details about CSS selector syntax, see the CSS selector specification.
Source
/**
* Finds the first descendant element of this document that matches the
* specified group of selectors.
*
* Unless your webpage contains multiple documents, the top-level
* [querySelector]
* method behaves the same as this method, so you should use it instead to
* save typing a few characters.
*
* [selectors] should be a string using CSS selector syntax.
*
* var element1 = document.querySelector('.className');
* var element2 = document.querySelector('#id');
*
* For details about CSS selector syntax, see the
* [CSS selector specification](http://www.w3.org/TR/css3-selectors/).
*/
Element querySelector(String selectors) => document.querySelector(selectors);