Automatically run the onsubmit="" function of forms when the enter key is pressed on the last input field.

form-keyboard-submit-jquery.js

$(() => {
    let update_form_listeners = () => {
        // Always check that the onsubmit attribute ends by return false; otherwise the page will reload
        $("form[onsubmit] input:last-of-type").each((index, element) => {
            if ($(element).parents('form').attr('onsubmit').substr(-13) !== 'return false;') {
                $(element).parents('form').attr('onsubmit', $(element).parents('form').attr('onsubmit')+'return false;');
            }
        });

        $("form[onsubmit] input:last-of-type").keypress((e) => {
            if (e.keyCode === 13) {
                $(e.target).parents('form').submit();
            }
        });
    };
    update_form_listeners();
    let observer = new MutationObserver(update_form_listeners);
    observer.observe(document, {
        subtree: true,
        childList: true,
        attributeFilter: ['form', 'input']
    });
});