Edit in JSFiddle

<button id="myButton">Button Click Here</button>
document.getElementById("myButton").onclick = function(){
    document.querySelector("body").innerHTML += "Classic Method <br>";
}

document.getElementById("myButton").addEventListener("click", function(){
    document.querySelector("body").innerHTML += "addEventListener1 <br>";
}, false);

document.getElementById("myButton").addEventListener("click", function(){
    document.querySelector("body").innerHTML += "addEventListener2 <br>";
}, false);