How to submit unchecked checkbox also

Question

If checkbox is not checked, clicking on form submit button does not submit any data.

Some checkboxes may be not present in form depending on form fields selected by

Answer 1

My form is created dynamically, so incorporating additional hidden fields would have been quite complicated. For me it works by temporarily altering the field type in a submit handler of the form.

myForm.addEventHandler("submit", ev => {
    for (let oField of ev.target.elements) {
        if (oField.nodeName.toUpperCase() === "INPUT" &&
                oField.type === "checkbox" &&
                ! oField.checked) {
            oField.type = "text";    // input type text will be sent
                         // After submitting, reset type to checkbox
            oReq.addEventListener("loadstart",
                        () => { oField.type = "checkbox"; });
        }
    }
});

This feels a bit dirty, but works for my.