js点击按钮div显示，点击div或者body和按钮，div隐藏

var box = document.getElementById("box");
var btn = document.getElementById("btn");
			
btn.onclick = function(event){
    event.stopPropagation();
    if(box.style.display == "none"){
        box.style.display = "block";
    }else{
        box.style.display = "none";
    }
};
window.onclick = function(){
    box.style.display = "none"
};            

　　前提是要给div加一个行内的display：none；