querySelector method
- @DomName('Document.querySelector')
 - @DocsEditable()
 
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
@DomName('Document.querySelector')
@DocsEditable()
Element querySelector(String selectors) =>
    _blink.BlinkDocument.instance.querySelector_Callback_1_(this, selectors);
    © 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
    https://api.dartlang.org/stable/1.24.3/dart-html/Document/querySelector.html