Use the id attribute in HTML to add the unique id of an element.
Example
You can try to run the following code to implement id attribute −
<html> <body> <h1>Tutorialspoint</h1> <p id = "myid">We provide Tutorials!</p> <button onclick = "display()">More...</button> <script> function display() { document.getElementById("myid").innerHTML = "We provide learning videos as well"; } </script> </body> </html>