Auto-Update Cart on Quantity Change

(function ($) {
    'use strict';

    if (typeof wc_cart_params === 'undefined') {
        return; // Not on the cart page.
    }

    $(document).ready(function () {
        // Visually hide the button; it is still used as the trigger.
        $('[name="update_cart"]').css({ opacity: 0, position: 'absolute', pointerEvents: 'none' });

        var timer;
        $(document).on('change', 'input.qty', function () {
            clearTimeout(timer);
            timer = setTimeout(function () {
                $('[name="update_cart"]').prop('disabled', false).trigger('click');
            }, 600);
        });
    });
}(jQuery));