demo：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
.box{width:200px;height: 300px;background: #ccc;position: absolute;left:0;top:0;display: none}
.box ul{margin: 0}
</style>
</head>
<body>
<!-- <a href="http://www.baidu.com">21321312</a> -->
<div class="box">
<ul>
<li>選項1</li>
<li>選項2</li>
<li>選項3</li>
<li>選項4</li>
</ul>
</div>
</body>
<script>
var obox = document.querySelector(".box")
document.oncontextmenu = function(eve){ //oncontextmenu 事件在元素中使用者右擊滑鼠時觸發并打開上下文菜單。
var e = eve || window.event;
obox.style.display = "block";
// return false;
// 取消預設事件
stopDefault(e);
obox.style.left = e.offsetX + "px";
obox.style.top = e.offsetY + "px";
}
document.onclick = function(){
obox.style.display = "none"
}
function stopDefault(e){
if(e.preventDefault){
e.preventDefault() //IE
}else{
e.returnValue = false; //GOOGLE
}
} //封裝函數
</script>
</html>
![web前端布局練手項目[圖]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)