以HH：mm格式计算时差
问题描述：
我有 HH：mm 格式的两个时间戳，我需要计算它们之间的差异，表示相同 HH中的时间间隔：mm format。
I have two timestamps in HH:mm format and I need to calculate difference between them representing the time interval in the same HH:mm format.
JavaScript中是否有任何实用程序可以实现此目的？我尝试使用 Date 对象，但我找不到有用的东西......你能帮助我吗？
Is there any utility in JavaScript to achieve this? I tried using Date object, but I cannot find something useful... Can you help me?
答
你可以直接减去两个日期，结果将是以毫秒为单位的差异。
You can just substract two Dates from one another, the result will be the difference in milliseconds.
// using static methods
var start = Date.now();
// the event you'd like to time goes here:
doSomethingForALongTime();
var end = Date.now();
var elapsed = end - start; // time in milliseconds
由于Date有一个构造函数接受毫秒作为参数，你可以重新通过这样做将其转换为日期
Since Date has a constructor that accepts milliseconds as an argument, you can re-convert this to a Date by just doing
var difference = new Date(elapsed);
//If you really want the hours/minutes,
//Date has functions for that too:
var diff_hours = difference.getHours();
var diff_mins = difference.getMinutes();