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));