Hi,

I would like to know how to check the current value and the previous value entered by user before changes.

for example, the form will allow user to enter customer number. The first time user enter 10 then change to 22

customer number : 10 -> change to 22

how do I get the previous value which is 10 in this case

You would have to store the previous value somewhere. Maybe when the page first loads you could add a custom property:

<input type="text" value="10" originalValue="10" />

Then in JavaScript read it:

var sOldValue = textbox.originalValue;

There is no built-in way to retrieve changed values.

Nicholas C. Zakas
Author, Professional JavaScript for Web Developers (ISBN 0764579088)
http://www.nczonline.net/