Need help Writing a little program with JavaScript

First, I want to create a "textarea" tag where the user can input some data, then I want to display the data back with "p" tag. The catch is for every sentence they write or if they end with a '.', '!' or '?' I want to count the number of words used and display a color for that specific sentence length and then move on the the next sentence and do the same thing.

Example:

http://ift.tt/2ybCB4I

if someone could write the code/logic behind this I would be grateful.