querySelector function
- 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.
Implementation
Element querySelector(String selectors) => document.querySelector(selectors);