如何从javascript中的日期中减去分钟数？ [英] How do I subtract minutes from a date in javascript?

问题描述

如何将此伪代码转换为工作js [不要担心结束日期的来源，除非它是一个有效的javascript日期]。

How can I translate this pseudo code into working js [don't worry about where the end date comes from except that it's a valid javascript date].

var myEndDateTime = somedate;  //somedate is a valid js date  
var durationInMinutes = 100; //this can be any number of minutes from 1-7200 (5 days)

//this is the calculation I don't know how to do
var myStartDate = somedate - durationInMuntes;

alert("The event will start on " + myStartDate.toDateString() + " at " + myStartDate.toTimeString());

推荐答案

一旦你知道这一点：

• 您可以通过调用日期。 com / Tutorial / JavaScript / 0240__Date / CreateDateobjectbycalltheconstructor.htmrel =noreferrer>构造函数，自1970年1月1日起以毫秒为单位。


• valueOf （） a 日期是自1970年1月1日以来的毫秒数。


• 有 60,000 一分钟内毫秒： - ]

• You can create a Date by calling the constructor with milliseconds since Jan 1, 1970.
• The valueOf() a Date is the number of milliseconds since Jan 1, 1970
• There are 60,000 milliseconds in a minute :-]

......它不是那么难。

...it isn't so hard.

在下面的代码中，通过从<$ c减去适当的毫秒数来创建新的 Date $ c> myEndDateTime ：

In the code below, a new Date is created by subtracting the appropriate number of milliseconds from myEndDateTime:

var MS_PER_MINUTE = 60000;
var myStartDate = new Date(myEndDateTime - durationInMinutes * MS_PER_MINUTE);

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