时间戳实现关闭页面和刷新的区别

<!DOCTYPE html><html lang="en"><head>  <meta charset="UTF-8">  <meta name="viewport" content="width=device-width, initial-scale=1.0">  <title>Document</title></head><body>    <script>var userAgent = navigator.userAgent; //取得浏览器的userAgent字符串  var isOpera = userAgent.indexOf("Opera") > -1; //判断是否Opera浏览器  var isIE = userAgent.indexOf("compatible") > -1 && userAgent.indexOf("MSIE") > -1 && !isOpera; //判断是否IE浏览器var isIE11 = userAgent.indexOf("rv:11.0") > -1; //判断是否是IE11浏览器var isEdge = userAgent.indexOf("Edge") > -1 && !isIE; //判断是否IE的Edge浏览器if(!isIE && !isEdge && !isIE11) {//兼容chrome和firefox  var _beforeUnload_time = 0, _gap_time = 0;  var is_fireFox = navigator.userAgent.indexOf("Firefox")>-1;//是否是火狐浏览器  window.onunload = function (){    _gap_time = new Date().getMilliseconds() - _beforeUnload_time;    if(_gap_time <= 5){        $.ajax({                type: "post",                url: "rule?wf_num=R_Z002_B021",                dataType: "json",                success: function(data){                    // var total =parseInt(data.total);                    // alert(111);                },                error:function(data){                    // alert("出错了");                }            });     }else{//浏览器刷新    }  }  window.onbeforeunload = function (){     _beforeUnload_time = new Date().getMilliseconds();    if(is_fireFox){//火狐关闭执行    }   };}  </script></body></html>