How do I make the same menu appear on every page of my website?

Question

For a website I'm making, I want to include the same menu on every webpage. It gets annoying to constantly copy and paste it into each HTML document and it forms a lot of clutter when reading the code. What is a good way to add it using a script? I hear I might be able to use PHP or a JavaScript library?

Answer 1

I always use php to do this.
You can put the code of menu in a text/html file and use include function on php.
<?php include ("menu.txt"); ?>
This way it be included as written just by one line of code.
PS:Remember that you will need to have a local/online server to test php.

Answer 2

I tried raw JavaScript, and it works, but my code seems messy. It also stop ssome features of the webpages from working.

var menuHTML = new XMLHttpRequest();
menuHTML.onreadystatechange = function() {
  if (this.readyState == 4 && this.status == 200) {
   var menuCode = menuHTML.responseText;
   document.getElementById("layout").innerHTML += menuCode;
  }
};
menuHTML.open("GET", "menu.html", true);
menuHTML.send();