js 日期与时间戳相互转换

1. 获取当天0点时间戳
   new Date(new Date().setHours(0, 0, 0, 0)).getTime() //获取当天00点时间戳
2. 时间戳转换成日期

     
      formatDate(time, count) {
        var date = new Date(Number(time));
        var year = date.getFullYear();
        var month = date.getMonth() + 1;
        var day = date.getDate();
        //  return year+"-"+month+"-"+day
        var h =
          (date.getHours() < 10 ? "0" + date.getHours() : date.getHours()) + ":";
        var m =
          date.getMinutes() < 10 ? "0" + date.getMinutes() : date.getMinutes();
        var s =
          date.getSeconds() < 10 ? "0" + date.getSeconds() : date.getSeconds();
        if (count == 0) {
          return h + m;
        } else if (count == 1) {
          return (
            year +
            "-" +
            (String(month).length > 1 ? month : "0" + month) +
            "-" +
            (String(day).length > 1 ? day : "0" + day) +
            " " +
            h +
            m
          );
        } else if(count==2){
            return (
                year +
                "-" +
                (String(month).length > 1 ? month : "0" + month) +
                "-" +
                (String(day).length > 1 ? day : "0" + day))    }else {
          return (
            year +
            "-" +
            (String(month).length > 1 ? month : "0" + month) +
            "-" +
            (String(day).length > 1 ? day : "0" + day) +
            " " +
            h +
            m +
            ":" +
            s
          );
        }
      },

3. 时分秒转换成时间戳
   //时分秒转换时间戳 sumTime(item) { let startTime = new Date(item); var h = startTime.getHours(); h = h * 60 * 60 * 1000; var minute = startTime.getMinutes(); minute = minute * 60 * 1000; let timeSum = h + minute; return timeSum; },
4. 时分秒时间戳转换成时分
   diffTime(time){ let h=parseInt(Number(time)/1000/60/60%24) < 10 ?'0'+parseInt(Number(time)/1000/60/60%24): parseInt(Number(time)/1000/60/60%24) ; let m=parseInt(Number(time)/1000/60%60) <10 ?'0'+parseInt(Number(time)/1000/60%60) :parseInt(Number(time)/1000/60%60) ; // let s= parseInt(Number(time)/1000%60) return h+":"+m }