计算一个月的最后一天 [英] Calculate last day of month

问题描述

如果您在 Date.setFullYear 中提供 0 作为 dayValue，您将获得上个月的最后一天:

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 中引用了此行为.这是一个可靠的跨浏览器功能还是我应该寻找替代方法?

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使用 0 作为上个月的最后一天并不意味着他们会继续这样做，或者没有列出的浏览器会这样做，但它增加了可信度相信它应该在每个浏览器中以相同的方式工作.

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