var data_time = new Date();
var time = data_time.getFullYear() + "-" + ("" + (data_time.getMonth() + 101))
          .substring(1) + "-" + ("" + (data_time.getDate() + 100)).substr(1) + " " + ("" + (data_time.getHours() + 100))
          .substr(1) + ":" + ("" + (data_time.getMinutes() + 101)).substr(1) + ":" + ("" + (data_time.getSeconds() + 101)).substr(1);

function timeconvert(time) { //将后台的datetime类型数据转换：这里获取到的时间格式形如：2018-05-19T08:04:52.000+0000
  var d = new Date(time);
  var times = d.getFullYear() + "-" + ("" + (d.getMonth() + 101)).substring(1) + "-" + ("" + (d.getDate() + 100)).substr(1) +" " + ("" + (d.getHours() + 100)).substr(1) + ":" + ("" + (d.getMinutes() + 101)).substr(1);
  //    + ":" + ("" + (d.getSeconds() + 101)).substr(1);
  return times;
}

//转化为毫秒值
let date = new Date(2019, 06, 30).getTime();//任意的一个日期
let nowdate = new Date(data_time.getFullYear(), (data_time.getMonth() + 1), data_time.getDate()).getTime();//这是用第一个方法获取到的当前时间

//604800000为七天的毫秒值
if (nowdate + 604800000 > date) { //若选择时间在当前日期的7天之内或之前
    console.log("7天之内或之前");
} else { //若选择时间在当前日期的7天之后
    console.log("7天之后");                                
}