ElementList<Element> querySelectorAll(String selectors)

Finds all descendant elements of this document fragment that match the specified group of selectors.

selectors should be a string using CSS selector syntax.

var items = document.querySelectorAll('.itemClassName');

For details about CSS selector syntax, see the CSS selector specification.

Source 

ElementList<Element /*=T*/> querySelectorAll/*<T extends Element>*/(String selectors) =>
  new _FrozenElementList/*<T>*/._wrap(_querySelectorAll(selectors));