function handler(ev) {
const e = ev || window.event;
const target = e.target || e.srcElement;
this.classList.toggle('selected');
console.log(
`Geklickt auf Knoten mit ID "${target.id}"`
);
console.log(
`Event an Knoten mit ID "${this.id}"`
);
}
function init() {
const elements = document.querySelectorAll(
'.level1, ' +
'.level2, ' +
'.level3'
);
for (let i=0; i<elements.length; i++) {
elements[i].addEventListener(
'click',
handler,
false
);
}
}
document.addEventListener('DOMContentLoaded', init);