How to insert html file contents into another using javascript

<!DOCTYPE html>
<html>

  <head>
    <script src="https://www.w3schools.com/lib/w3.js"></script>
  </head>

  <body>
    <h1>Parent Container Page</h1>
    
    Below is my insertion point for foo.html
    <div w3-include-html="foo.html"></div>
    
        Below is my insertion point for bat.html
    <div w3-include-html="bar.html"></div>
    
  <script>
    w3.includeHTML();
  </script>
  
  </body>



</html>

// Code goes here

/* Styles go here */

<h2>This is the contents of foo.html</h2>

<div>
  Some random div
</div>

<a href="http://www.google.com">Link to google</a>

<h2>This is the contents of bar.html</h2>



<a href="http://www.yahoo.com">Link to yahoo</a>