计算一个时间离另一个时间间隔多长时间

let hover = thisObj.time.substring(0, thisObj.time.indexOf(':'))
let minutes = thisObj.time.substring(thisObj.time.indexOf(':') + 1)
let dateHover = thisObj.dateTime.substring(0, thisObj.time.indexOf(':'))
let dateMinutes = thisObj.dateTime.substring(thisObj.time.indexOf(':') + 1)
let num = parseInt(hover * 60 + parseInt(minutes))
let dateNum = parseInt(dateHover * 60 + parseInt(dateMinutes))
let hoverNum = parseInt((dateNum - num) / 60)
let minutesNum = parseInt((dateNum - num) - hoverNum * 60)
alert(阅读提醒将在' + hoverNum + '小时' + minutesNum + '分钟后提醒)