definedEvts.js

//defined function
function doSomething(msg){
 alert(msg);
}

//attach event for h1 elements
document.querySelector('h1').onclick = function () {
 doSomething('h1: Event OnClick attached');
};

//attach event with addeventlistener
function attachHtmlEvents(){
 var e = document.getElementById('someid');
 e.addEventListener('click', doSomething('Event attached'), false);
}