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.
Element querySelector(String selectors) native;
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Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/2.0.0/dart-html/Document/querySelector.html