<button id="btn1">点击显示div</button>

<div id="showDiv">

    显示了

</div>

window.onload = function(){

    var btn1 = document.getElementById("btn1");

    var showDiv = document.getElementById("showDiv");

    btn1.onclick = function(ev){

        var oEvent = ev || event;

        showDiv.style.display = "block";

        //阻止时间冒泡

        oEvent.cancelBubble = true;

    }

    document.onclick = function(){

        showDiv.style.display = "none";

    }

}