js时间对比-转化为几天前,几小时前，几分钟前

 function getDateDiff(dateTimeStamp){
     var minute = 1000 * 60;
     var hour = minute * 60;
     var day = hour * 24;
     var halfamonth = day * 15;
     var month = day * 30;
     var now = new Date().getTime();
     var diffValue = now - dateTimeStamp;
     if(diffValue < 0){return;}
     var monthC = diffValue/month;
     var weekC = diffValue/(7*day);
     var dayC = diffValue/day;
     var hourC = diffValue/hour;
     var minC = diffValue/minute;
     if(monthC >= 1){
         result = parseInt(monthC) + "月前";
     }else if(weekC >= 1){
         result = parseInt(weekC) + "周前";
     }else if(dayC >= 1){
         result = parseInt(dayC) +"天前";
     }else if(hourC >= 1){
         result = parseInt(hourC) +"小时前";
     }else if(minC >= 1){
         result = parseInt(minC) +"分钟前";
     }else{
         result = "刚刚";
     }
     return result;
 }

转换标准时间为时间戳：

 function getDateTimeStamp(dateStr){
     return Date.parse(dateStr.replace(/-/gi,"/"));
 }

调用：

 var timeStr = '2018-05-16 15:02:20',
       timeStamp = getDateTimeStamp(timeStr);
 console.log(getDateDiff(timeStamp));