JavaScript - websites to use

Forking the Super-Calculator
Follow these steps to open the Super-Calculator and to make your own version of it:

Open your web browser and login at http://jsfiddle.net.
Go to our public dashboard at http://jsfiddle.net/user/forkids/fiddles and locate the program called Chapter 9 – Super-Calculator, or go directly to the Super-Calculator at http://jsfiddle.net/forkids/LdtbfnL0.

Click the Fork button in the top menu to make a copy of the Super-Calculator in your own JSFiddle account.
Use the Fiddle Options in the left menu to change the name of your Super-Calculator to (Your Name)’s Super-Calculator.
Click Update in the top menu, and then click Set as Base.