javascript - onkeyup Event Firing delay -

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i have input textbox people enter username, has onkeyup event attribute attached fires off ajax request check if username taken.

  1. what delay between first key second ? meaning if type 5 letter word 1 letter after other. ajax fire 5 times ?

  2. if there no delay, "computationally expensive" since there many database queries ? or there no noticeable difference ?

  3. if there difference in performance, methods take using javascript check if user "done" typing. still want automatically check after typing. ruling out onblur attributes etc.

my code: http://pastebin.com/hxfgk7nl
(code indentation wasn't working me on stack overflow)

yes, fire every key-up event. can reduce performance hit using following approach.

  1. i sure must have minimum character length username. wait until user type number of characters query database.

  2. you bring usernames starting user typed username , process in local memory. may not real time reduce number database queries. depend on size of current user list.

  3. double check existence of username before saving database.


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