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

This is what I came up with in https://github.com/liberapay/liberapay.com/pull/875:

$('form').on('submit', function (e) {
    var $form = $(this);
    // Check that the form hasn't already been submitted
    if ($form.data('js-submit-disable')) {
        e.preventDefault();
        return false;
    }
    // Prevent submitting again
    $form.data('js-submit-disable', true);
    // Set a timer to disable inputs for visual feedback
    var $inputs = $form.find(':not(:disabled)');
    setTimeout(function () { $inputs.prop('disabled', true); }, 100);
    // Unlock if the user comes back to the page
    $(window).on('focus pageshow', function () {
        $form.data('js-submit-disable', false);
        $inputs.prop('disabled', false);
    });
});