计算每月的最后一天 [英] Calculate last day of month

问题描述

如果在 Date.setFullYear 中提供 0 作为 dayValue ，则会得到上个月的最后一天:

If you provide 0 as the dayValue in Date.setFullYear you get the last day of the previous month:

d = new Date(); d.setFullYear(2008, 11, 0); //  Sun Nov 30 2008

在 mozilla 上对此行为有参考.这是可靠的跨浏览器功能还是我应该考虑替代方法?

There is reference to this behaviour at mozilla. Is this a reliable cross-browser feature or should I look at alternative methods?

推荐答案

var month = 0; // January
var d = new Date(2008, month + 1, 0);
console.log(d.toString()); // last day in January

IE 6:                     Thu Jan 31 00:00:00 CST 2008
IE 7:                     Thu Jan 31 00:00:00 CST 2008
IE 8: Beta 2:             Thu Jan 31 00:00:00 CST 2008
Opera 8.54:               Thu, 31 Jan 2008 00:00:00 GMT-0600
Opera 9.27:               Thu, 31 Jan 2008 00:00:00 GMT-0600
Opera 9.60:               Thu Jan 31 2008 00:00:00 GMT-0600
Firefox 2.0.0.17:         Thu Jan 31 2008 00:00:00 GMT-0600 (Canada Central Standard Time)
Firefox 3.0.3:            Thu Jan 31 2008 00:00:00 GMT-0600 (Canada Central Standard Time)
Google Chrome 0.2.149.30: Thu Jan 31 2008 00:00:00 GMT-0600 (Canada Central Standard Time)
Safari for Windows 3.1.2: Thu Jan 31 2008 00:00:00 GMT-0600 (Canada Central Standard Time)

输出差异是由于 toString()实现方式的差异，而不是因为日期不同.

Output differences are due to differences in the toString() implementation, not because the dates are different.

当然，仅仅因为上面标识的浏览器将0用作上个月的最后一天，并不意味着它们会继续这样做，或者未列出的浏览器也会这样做，但这为相信它在每种浏览器中都应该以相同的方式工作.

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