moodle-local_treestudyplan/amd/src/util/formfields.js

/**
 * convert a text field into an integer only text field
 * @param {string} id The Id of the form field
 * @param {bool} unsigned Allow only unsigned values
 */
export function text_integer(id,unsigned=false){
    const element = document.getElementById(id);

    if (element) {
        element.addEventListener("input",() => {
            var val = element.value;
            if (val != '') {
                if ((isNaN(val) && !(!unsigned && val == '-')) || (unsigned && val < 0)) {
                    // Set input value empty
                    if (unsigned) {
                        element.value = val.replace(/[^0-9]/g,'');
                    } else {
                        element.value = val.replace(/[^0-9-]/g,'').replace(/(.{1})(-)/g,'$1');
                    }
                    return false;
                } else {
                    return true;
                }
            }
        });
    }
}