document.onclick = function(){ ... }
is the same as
document.addEventListener("click", function(){ ... })
var anchors = document.getElementsByTagName('a');
for (var anchor = 0; anchor < anchors.length; ++anchor){
anchors[anchor].onclick = function() {
this.classList.toggle('active');
}
}
Instead of
document.getElementById('element').addEventListener('CLICK', function(){ ... });
document.getElementById('element').addEventListener('SUBMIT', function(){ ... });
document.getElementById('element').addEventListener('HOVER', function(){ ... });
you can use mapping to bind multiple events:
"CLICK SUBMIT HOVER".split(" ").map(
name => document.getElementById(key).addEventListener(name, function(){ ... })
);