You can add multiple only by code even if you have the second onclick
atribute in the html it gets ignored, and click2 triggered
never gets printed, you could add one on action the mousedown
but that is just an workaround.
So the best to do is add them by code as in:
var element = document.getElementById("multiple_onclicks");_x000D_
element.addEventListener("click", function(){console.log("click3 triggered")}, false);_x000D_
element.addEventListener("click", function(){console.log("click4 triggered")}, false);
_x000D_
<button id="multiple_onclicks" onclick='console.log("click1 triggered");' onclick='console.log("click2 triggered");' onmousedown='console.log("click mousedown triggered");' > Click me</button>
_x000D_
You need to take care as the events can pile up, and if you would add many events you can loose count of the order they are ran.