Firebug dynamically executes JavaScript

You can use Firebug to write and execute a JavaScript in real time.

This is for testing and making sure the script is working properly, and is a good way to deploy your JavaScript code before deploying it to production.

Open Firebug > Script (Script) > Display the command line, the code is as follows:

alert("w3cschool.cc")

After pressing the Enter key, you can immediately See the output of the code. as the picture shows: