document get element by id w3schools code example

Example 1: change innerhtml

document.getElementById("p1").innerHTML = "New text!";

Example 2: html how to get js

<!--Use The <script> tag to impliment javascript. You can put script 
tags in the head or body tags or both. Though most people should put
there script tags in the head tag-->
<script>
  console.log("Javascript");
</script>