Here is a basic “Hello World!” exercise in Javascript. Online code editors like JSFiddle and Codepen truly come into their own when learning Javascript.
This simple example uses Javascript’s alert method to display a “pop-up” type message when the page loads (this is not a good thing to do on your website, by the way). Check it out in this Fiddle (click on the Result tab to load the page and run the script):
Or copy-paste the below code into an HTML file and fire up your browser!
<html>
<head>
<title>Hello World! Javascript</title>
</head>
<body>
<h1>Hello World! Javascript</h1>
<script>
alert("Hello World!");
</script>
</body>
</html>
Javascript code can be written in your HTML files between the <script> tags. The <script> tags are in turn nested in the <head> or <body> tags.
Your next step is to use an event to fire your Javascript code. Head on over to the post Javascipt’s onclick() event.