Make header and footer files to be included in multiple html pages

Must you use html file structure with JavaScript? Have you considered using PHP instead so that you can use simple PHP include object?

If you convert the file names of your .html pages to .php - then at the top of each of your .php pages you can use one line of code to include the content from your header.php

<?php include('header.php'); ?>

Do the same in the footer of each page to include the content from your footer.php file

<?php include('footer.php'); ?>

No JavaScript / Jquery or additional included files required.

NB You could also convert your .html files to .php files using the following in your .htaccess file

# re-write html to php
RewriteRule ^(.*)\.html$ $1.php [L]
RewriteRule ^(.+)/$ http://%{HTTP_HOST}/$1 [R=301,L]


# re-write no extension to .php
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^\.]+)$ $1.php [NC,L]

I add common parts as header and footer using Server Side Includes. No HTML and no JavaScript is needed. Instead, the webserver automatically adds the included code before doing anything else.

Just add the following line where you want to include your file:

<!--#include file="include_head.html" -->

You can accomplish this with jquery.

Place this code in index.html

<html>
<head>
<title></title>
<script
    src="https://code.jquery.com/jquery-3.3.1.js"
    integrity="sha256-2Kok7MbOyxpgUVvAk/HJ2jigOSYS2auK4Pfzbm7uH60="
    crossorigin="anonymous">
</script>
<script> 
$(function(){
  $("#header").load("header.html"); 
  $("#footer").load("footer.html"); 
});
</script> 
</head>
<body>
<div id="header"></div>
<!--Remaining section-->
<div id="footer"></div>
</body>
</html>

and put this code in header.html and footer.html, at the same location as index.html

<a href="http://www.google.com">click here for google</a>

Now, when you visit index.html, you should be able to click the link tags.