var start = new Date(new Date(new Date().toLocaleDateString()).getTime());

  console.log(start); //Fri Feb 23 2018 00:00:00 GMT+0800 (中国标准时间)

  var start = new Date(new Date(new Date().toLocaleDateString()).getTime() + 24 * 60 * 60 * 1000 - 1);

  console.log(start); //Fri Feb 23 2018 23:59:59 GMT+0800 (中国标准时间)

var endTime = new Date()

let oneHourLater = endTime.getTime() + 60 * 60 * 1000 //一个小时倒计时

let fourDayLater = endTime.getTime() + 60 * 60 * 1000 * 4 * 24  //4天倒计时

endTime.setTime(oneHourLater)

endTime.setTime(fourDayLater)

// 为 <div> 元素添加 class:

document.getElementById("myDIV").classList.add("mystyle");

// 为 <div> 元素添加多个类:

document.getElementById("myDIV").classList.add("mystyle", "anotherClass", "thirdClass");

// 为 <div> 元素移除一个类:

document.getElementById("myDIV").classList.remove("mystyle");

// 为 <div> 元素移除多个类:

document.getElementById("myDIV").classList.remove("mystyle", "anotherClass", "thirdClass");

// 检查是否含有某个CSS类

myDiv.classList.contains('myCssClass'); //return true or false

var mystring ="jb51.net,google.com,baidu.com_weibo.com_haotu.net";

var myarray = mystring.split(/[,_]/);