Checking password match while typing

Probably invalid syntax in your onChange event, I avoid using like this (within the html) as I think it is messy and it is hard enough keeping JavaScript tidy at the best of times.

I would rather register the event on the document ready event in javascript. You will also definitely want to use keyup event too if you want the validation as the user is typing:

$(document).ready(function () {
   $("#txtConfirmPassword").keyup(checkPasswordMatch);
});

Here is a working example

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Personally I would prefer to do the check when either password field changes, that way if they re-type the original password then you still get the same validation check:

$(document).ready(function () {
   $("#txtNewPassword, #txtConfirmPassword").keyup(checkPasswordMatch);
});

Here is a working example