The default editor that comes with the UNIX operating system is called vi (visual editor). Do you want to learn or try the powerful Vi editor? you can give the online Vi editor a try . It is an an online vi clone written using JavaScript.
Regarding vi compatibility, jsvi supports almost all vi-keys, and almost all ed/ex (:) commands including :hardcopy, and :g//m0 but noticeably missing are :i and commands that work similar to it, as well as certain register operations.
You can have a look on it here - http://gpl.internetconnection.net/vi/
If you are a beginner and want to have a look on the Basic vi Commands , this article is a good one, to learn about it. It includes basic commands for
Start and Exit Vi
Moving the cursor
Screen Manipulation
Text Add, Edit, delete, cut, copy and paste
Search
Saving