具有Moment(date)元素的数组排序 [英] Sorting of array with Moment(date) elements

问题描述

我有一个数组，其中填充了moment(数据库提供的日期)元素.我正在尝试对数组进行排序，以使第一个元素是最旧的，而最后一个元素是最新的，但是没有成功.

I have an array that is populated with moment(Date provided by the database) elements. I am trying to sort the array so that the first element is the oldest and the last element is the newest, but with no success.

     for (let item of items) {

            dates.push(moment(item.created));
          }
          dates.sort(function(a,b){
            var da = new Date(a).getTime();
            var db = new Date(b).getTime();

            return da < db ? -1 : da > db ? 1 : 0
          });
    }
  console.log(dates);

这总是打印当前时间乘以元素数.

This always prints the current time times number of elements.

推荐答案

这比您想象的要容易得多. :-)当在作为Moment实例的操作数上使用-时，它们将被强制转换为数字，即它们的毫秒数(自Epoch以来的值).所以:

It's much easier than you think. :-) When you use - on a operands that are Moment instance, they're coerced to numbers, which are their milliseconds-since-the-Epoch value. So:

dates.sort((a, b) => a - b);

...对它们进行升序排序(最早的日期在前)，并且

...sorts them ascending (earliest dates first), and

dates.sort((a, b) => b - a;

...对它们进行降序排序(最新日期在前).

...sorts them descending (latest dates first).

我很高兴在那里使用了简洁的箭头功能，因为您已经在代码中使用了ES2015 +功能.

I've happily used concise arrow functions there, since you're already using ES2015+ features in your code.

示例:

let dates = [
  moment("2017-01-12"),
  moment("2018-01-12"),
  moment("2017-07-12"),
  moment("2016-07-30")
];
dates.sort((a, b) => a - b);
console.log(dates);

dates = [
  moment("2017-01-12"),
  moment("2018-01-12"),
  moment("2017-07-12"),
  moment("2016-07-30")
];
dates.sort((a, b) => b - a);
console.log(dates);

.as-console-wrapper {
  max-height: 100% !important;
}

The built-in Stack Snippets console shows Moment instances by calling toString, which shows is the ISO date string. But they're Moment instances (you can see that in the browser's real console).
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.22.2/moment.min.js"></script>

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