How can I prevent a double submit with jQuery or Javascript?

Question

I keep getting duplicate entries in my database because of impatient users clicking the submit button multiple times.

I googled and googled and found a few scripts,

Answer 1

If you are using client-side validation and want to allow additional submit attempts if the data is invalid, you can disallow submits only when the form content is unchanged:

var submittedFormContent = null;
$('#myForm').submit(function (e) {
    var newFormContent = $(this).serialize();
    if (submittedFormContent === newFormContent)
        e.preventDefault(true);
    else 
        submittedFormContent = newFormContent;
});