Use the async attribute to set the script to execute asynchronously as and when it is available. It only uses the external script.
Firstly, add a js file. Let us give it a name, new.js,
function sayHello() {
alert("Hello World")
}Let’s add the HTML code now and execute the above script −
<html> <head> <script src = "new.js" ></script> </head> <body> <p>This is demo text.</p> </body> </html>