how to prompt a 'leave the page' alert if the user typed in the textbox and attempted to leave the page?(like facebook)

[darkfox]

hey guys! i need help!

 

i want to make the pages prompt an alert if the user tried to leave the page/textbox that he is currently editing.

 

i want to make it like the facebook type, like if you type something in the post section of facebook then tried to leave or click the back button in the browser..

 

 

please help me guys.. can it be done by PHP or Javascript? please let me know and please help me! thanks guys! cheers..

 

[Jessica]

That's JavaScript. You should be able to google it and find plenty of examples.