query selector all multiple code example

Example 1: class query css js all

var matches = document.querySelectorAll("div.note, div.alert");

Example 2: queryselectorall of multiple tags

Yes, because querySelectorAll accepts full CSS selectors,
and CSS has the concept of selector groups, which lets you specify 
more than one unrelated selector. For instance:

var list = document.querySelectorAll("form, p, legend");

...will return a list containing any element that is a form or p or legend.

CSS also has the other concept: Restricting based on more criteria. 
You just combine multiple aspects of a selector. For instance:

var list = document.querySelectorAll("div.foo");

...will return a list of all div elements that also (and) 
have the class foo, ignoring other div elements.

You can, of course, combine them:

var list = document.querySelectorAll("div.foo, p.bar, div legend");

...which means "Include any div element that also has the foo class,
any p element that also has the bar class, and any legend element 
thats also inside a div."