js日期减去日期算出剩余的天数

 this.list[0].expiryStartTime = '2019=09-02 16:23:50' // 日期格式

var beginDate = new Date(this.list[i].expiryStartTime).getTime()
var endDate = new Date(this.list[i].expiryEndTime).getTime()
                                var days = (endDate - beginDate) / (1 * 24 * 60 * 60 * 1000);
                                this.list[i].lastsTime = days