1//Pretend there is a <p> with class "example"
2const myParagraph = document.querySelector('.example');
3//You can do many this with is
4myParagraph.textContent = 'This is my new text';

1/*The querySelector() method returns the first element that matches a specified 
2CSS selector(s) in the document. Note: The querySelector() method only returns 
3the first element that matches the specified selectors. To return all the 
4matches, use the querySelectorAll() method instead.*/
5
6// for example 
7
8//for class
9document.querySelector(".ClassName")
10
11// for id 
12document.querySelector("#ID")
13
14// etc.

1const elt = document.querySelector("#myId p.article > a");
2

1// TO select all the h1 from Html
2document.querySelectorAll("h1")
3
4//To select h1 from a particular class or id
5document.querySelector(".className/#id h1")

1var element = document.querySelector("#myid .myclass p");
2

1<div id="foo\bar"></div>
2<div id="foo:bar"></div>
3
4<script>
5  console.log('#foo\bar');               // "#fooar" (\b is the backspace control character)
6  document.querySelector('#foo\bar');    // Does not match anything
7
8  console.log('#foo\\bar');              // "#foo\bar"
9  console.log('#foo\\\\bar');            // "#foo\\bar"
10  document.querySelector('#foo\\\\bar'); // Match the first div
11
12  document.querySelector('#foo:bar');    // Does not match anything
13  document.querySelector('#foo\\:bar');  // Match the second div
14</script>