html-includes

include html file in html file, a workaround

index.htm : main file
it has 2div elements to hold the contents to be included
the other 2files are:
header.js , footer.js

Also other ways:
https://css-tricks.com/the-simplest-ways-to-handle-html-includes/

using w3schools appml
https://www.w3schools.com/appml/appml_includes.asp

using w3schools w3js
https://www.w3schools.com/w3js/w3js_html_include.asp