原生js自定义右键菜单

<!--start右键菜单的结构-->
<div id="rightmenu" class="rightmenu">
 <ul>
  <li disabled="disabled">
        <a href="#" >返回(B)</a> 
        <span>Alt+向左箭头</span></li>
  <li><a href="#" >前进(F)</a> <span>Alt+向右箭头</span></li>
  <li><a href="#" >重新加载(R)</a> <span>Ctrl+R</span></li>
 </ul>
 <ul>
  <li><a href="#" >另存为(A)...</a> <span>Ctrl+S</span></li>
        <li><a href="#" >打印(P)..</a> <span>Ctrl+P</span></li>
  <li><a href="#" >投射(C)...</a> <span>Ctrl+R</span></li>
 </ul>
 <ul>
  <li><a href="#" >查看你个锤代码(V)</a> <span>Ctrl+U</span></li>
     <li><a href="#" >检查你个瓜皮(N)</a> <span>Ctrl+Shift+L</span></li>
 </ul>
</div>
<!--end右键菜单的结构-->
  
<div class="box"></div>

*{
 margin: 0;
 padding: 0;
}
li{
 list-style: none;
}
.rightmenu{
 width: 250px;
 background: #fff;
 border: 1px solid #bababa;
 position: fixed;
 box-sizing: border-box;
 display: none;
}
.rightmenu ul{
 border-bottom: 1px solid #e9e9e9;   
}
.rightmenu ul li{
 height: 30px;
 line-height: 30px;
 color: #000;
 padding: 0 25px;
 box-sizing: border-box;
 margin: 2px 0;
     cursor: default;
}
.rightmenu ul li:hover{
 background: #ebebeb;
}
.rightmenu ul li a{
 font-size: 12px;
 color: #000;
 cursor: default;
 text-decoration: none;
}
.rightmenu ul li span{
 float: right;
 font-size: 12px;
 color: #000;
}
.box{
 width: 100px;
 height: 100px;
 background: red;
}

<script>
 document.addEventListener('DOMContentLoaded',function(){
 //获取
 var rightMenu=document.getElementById('rightmenu');
 //1.首先将右键默认行为关闭
 window.oncontextmenu=function(event){
  event.preventDefault();
  //2.设置右键行为
  rightMenu.style.display="none";//重置已经block的菜单
  rightMenu.style.display="block";
  rightMenu.style.left=event.offsetX+'px';
   rightMenu.style.top=event.offsetY+'px';
  }
  //3.根据真实浏览器的右键来看左键是可以取消右键菜单的
  document.onclick=function(event){
   rightMenu.style.display="none";
  }
  //4.功能并不完善,需要给每个li写BOM事件,这里暂时不写了
  //5.仔细检查你会发现当右键在自己定义的右键菜单上时,会出现一点小情况,可以自己测试
    })
</script>