window.addEventListener('load', function (e) {
    // Get all numeric fields.
    let fields = document.querySelectorAll('[inputmode = "numeric"]');

    // The localize function.
    let localize = function (value) {
        if (value === '') {
            return value; // Otherwise the fields would have 'NaN' values... Nah!!!
        }
        let n = parseInt(value.replace(/\D/g, ''));
        return n.toLocaleString('nl-NL');
    };

    // Loop fields and add event listeners for keyup and onload.
    for (let field of fields) {
        field.addEventListener('keyup', function (event) {
            let value = event.target.value;
            event.target.value = localize(value);
        }, false);
        field.value = localize(field.value);
    }
});