onkeyup事件触发延迟

Question

I have a input textbox for people to enter a username, it has a onkeyup event attribute attached which fires off an AJAX request to check if the username is taken.

1. What is the delay between the first key to the second ? Meaning if I type a 5 letter word one letter after the other. Does the AJAX fire 5 times ?

2. If there is no delay, would this be "computationally expensive" since there would so many database queries ? Or would there be no noticeable difference ?

3. If there is a difference in performance, what methods could I take using Javascript to check if the user is actually "done" typing. I still want it to automatically check after typing. Thus ruling out onblur attributes etc.

My Code: http://pastebin.com/hXfgk7nL
(code indentation wasn't working for me on stack overflow)

Answer 1

yes it will fire. if you don't need that means, you have to check conditions with a flag. check the given value with the previous value which is stored in a variable.