事件：onclick
属性：display
利用if语句实现
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
<title>Examples</title>
<meta name="description" content="">
<meta name="keywords" content="">
<link href="css1.css" rel="stylesheet" type="text/css"
charset="UTF-8">
</head>
<body>
<input id="btn1" type="button" value="显示隐藏"/>
<div id="div1"></div>
<script src="js1.js"> </script>
</body>
</html>
//////////////////css
#div1{
display:none;
width:100px;
height:300px;
background:green;
}
////////////////////js
var oBtn=document.getElementById("btn1");
oBtn.onclick=function(){
var oDiv=document.getElementById("div1");
if(oDiv.style.display=="none"){
oDiv.style.display="block";
}
else{
oDiv.style.display="none";
}
};