检测“无效日期"JavaScript 中的日期实例 [英] Detecting an "invalid date" Date instance in JavaScript

问题描述

我想区分 JS 中的有效日期对象和无效日期对象，但不知道如何区分:

I'd like to tell the difference between valid and invalid date objects in JS, but couldn't figure out how:

var d = new Date("foo");
console.log(d.toString()); // shows 'Invalid Date'
console.log(typeof d); // shows 'object'
console.log(d instanceof Date); // shows 'true'

对于编写 isValidDate 函数有什么想法吗?

Any ideas for writing an isValidDate function?

• Ash 推荐使用 Date.parse 来解析日期字符串，它提供了一种权威的方式来检查日期字符串是否有效.
• 如果可能的话，我希望我的 API 接受一个 Date 实例，并且能够检查/断言它是否有效.Borgar 的解决方案可以做到这一点，但我需要跨浏览器对其进行测试.我也想知道有没有更优雅的方式.
• Ash 让我考虑完全不让我的 API 接受 Date 实例，这将最容易验证.
• Borgar 建议测试 Date 实例，然后测试 Date 的时间值.如果日期无效，则时间值为 NaN.我检查了 ECMA-262 并且这种行为符合标准，这正是我正在寻找的.

• Ash recommended Date.parse for parsing date strings, which gives an authoritative way to check if the date string is valid.
• What I would prefer, if possible, is have my API accept a Date instance and to be able to check/assert whether it's valid or not. Borgar's solution does that, but I need to test it across browsers. I also wonder whether there's a more elegant way.
• Ash made me consider not having my API accept Date instances at all, this would be easiest to validate.
• Borgar suggested testing for a Date instance, and then testing for the Date's time value. If the date is invalid, the time value is NaN. I checked with ECMA-262 and this behavior is in the standard, which is exactly what I'm looking for.

推荐答案

我会这样做:

if (Object.prototype.toString.call(d) === "[object Date]") {
  // it is a date
  if (isNaN(d.getTime())) {  // d.valueOf() could also work
    // date is not valid
  } else {
    // date is valid
  }
} else {
  // not a date
}

更新 [2018-05-31]:如果您不关心来自其他 JS 上下文(外部窗口、框架或 iframe)的 Date 对象，可能更喜欢这种更简单的形式:>

Update [2018-05-31]: If you are not concerned with Date objects from other JS contexts (external windows, frames, or iframes), this simpler form may be preferred:

function isValidDate(d) {
  return d instanceof Date && !isNaN(d);
}

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