原生JS绑定为同一元素多个事件

var btn=document.getElementById("btn");
btn.onclick=f1;
btn.onmouseover=f1;
btn.onmouseout=f1;
function f1(e) {    
	switch (e.type)    {        
		case "click":
			console.log("click触发");
			break;        
		case  "mouseover":
			console.log("mouseover触发");
			break;        
		case  "mouseout":
			console.log("mouseout触发");
			break;    
	}
}