A first splash into JavaScript
Now you've learned something about the theory of JavaScript and what you can do with it, we are going to give you an idea of what the process of creating a simple JavaScript program is like, by guiding you through a practical tutorial. Here you'll build up a simple "Guess the number" game, step by step.
Ref: https://developer.mozilla.org/en-US/docs/Learn/JavaScript/First_steps/A_first_splash