function checkAgeNotNegative() {
const myElement = document.getElementById('age');
const age = myElement.value;
if (age < 0) {
showMessage('Alter kann nicht negativ sein.');
}
}
function checkAgeIsNumber() {
const myElement = document.getElementById('age');
const age = myElement.value;
if(!(!isNaN(parseFloat(age)) && isFinite(age))) {
showMessage('Alter muss Zahl sein.');
}
}
function clearMessage() {
showMessage('');
}
function showMessage(message) {
const output = document.getElementById('output');
output.textContent = message;
}
function init() {
const myElement = document.getElementById('age');
myElement.addEventListener('blur', clearMessage);
myElement.addEventListener('blur', checkAgeNotNegative);
myElement.addEventListener('blur', checkAgeIsNumber);
const checkBox = document.getElementById('validation');
checkBox.addEventListener('change', function() {
if (checkBox.checked) {
console.log('checked');
myElement.addEventListener('blur', checkAgeNotNegative);
myElement.addEventListener('blur', checkAgeIsNumber);
} else {
console.log('unchecked');
clearMessage(),
myElement.removeEventListener('blur', checkAgeNotNegative);
myElement.removeEventListener('blur', checkAgeIsNumber);
}
}
);
}
document.addEventListener('DOMContentLoaded', init);