How to change the content of text_area_tag on client side

dear all,

I have a text_area_tag. And I want to provide a link. When user click on
it.

It will change the content of this text_area_tag. And I would like the
change

is done on client side. It May using such as Java Script , but not
using AJAX or

return to the controller of my server side. Then back the change of
content of

text_area_tag to client.

any tips is appreciated.

-Feng