Default example

<h1>demo</h1>
h1 { color: red; }
console.log(document.querySelectorAll('h1'));

Multiple example

<h1>demo</h1>
h1 { color: red; }
console.log(document.querySelectorAll('h1'));
<h1>demo</h1>
h1 { color: red; }
console.log(document.querySelectorAll('h1'));