使用 underscore.js 按值对对象数组进行排序 [英] Sort array of objects by value using underscore.js

问题描述

我正在尝试按 average 属性按降序对对象数组进行排序 - 因此最大的 average 排在第一位 - 但我无法使用下划线.js.以下是我的尝试:

I'm trying to sort an array of objects by the average property in descending order - so the largest average is first - but am not able to using underscore.js. Below is my attempt:

var jsonData = [
{
    "title": "Dear Kitten",
    "totalCount": 1689,
    "average": 241
},
{
    "title": "Weird Things All Couples Fight About",
    "totalCount": 9966,
    "average": 1424
},
{
    "title": "If Disney Princesses Were Real",
    "totalCount": 16567,
    "average": 2367
},
{
    "title": "Secret Tricks With Everyday Objects",
    "totalCount": 24884,
    "average": 3555
},
{
    "title": "The Coolest Travel Hacks",
    "totalCount": 41847,
    "average": 8369
},
{
    "title": "5 Ways You're Drinking Coffee Wrong",
    "totalCount": 55673,
    "average": 7953
},
{
    "title": "The Perfect Way To Pour A Beer",
    "totalCount": 58097,
    "average": 58097
},
{
    "title": "Fruit You're Eating Wrong",
    "totalCount": 65570,
    "average": 32785
},
{
    "title": "Your Cat Is Judging You",
    "totalCount": 78952,
    "average": 11279
},
{
    "title": "3rd Date vs 30th Date",
    "totalCount": 84394,
    "average": 14066
}
];

console.log(_.sortBy(jsonData, "average"));

jsFiddle

推荐答案

这里的问题是您希望数组按照 average 以降序顺序排序，而不是默认升序.

The issue here is that you wanted the array to be sorted in descending order by average, instead of the default ascending order.

您可以通过为 _.sortBy() 函数提供自定义 iteratee 来实现:

You could do this by providing a custom iteratee to the _.sortBy() function:

_.sortBy( jsonData, function( item ) { return -item.average; } )

更新小提琴

但我不建议这样做.简单地使用原生 JavaScript [].sort() 方法并为其提供一个比较函数会更好:

But I don't recommend that. It would be much better to simply use the native JavaScript [].sort() method and provide it a comparison function:

jsonData.sort( function( a, b ) { return b.average - a.average; } )

更好的小提琴

如果您对一个非常大的数组进行排序，这也比使用 _.sortBy() 更快.查看 _.sortBy() 的源代码以了解原因:

If you were sorting a very large array, this would also be faster than using _.sortBy(). Look at the source code for _.sortBy() to see why:

_.sortBy = function(obj, iteratee, context) {
  iteratee = cb(iteratee, context);
  return _.pluck(_.map(obj, function(value, index, list) {
    return {
      value: value,
      index: index,
      criteria: iteratee(value, index, list)
    };
  }).sort(function(left, right) {
    var a = left.criteria;
    var b = right.criteria;
    if (a !== b) {
      if (a > b || a === void 0) return 1;
      if (a < b || b === void 0) return -1;
    }
    return left.index - right.index;
  }), 'value');
};

除了 .sort() 调用之外，它还做了很多工作——而这段代码只是冰山一角，它调用的辅助函数就像 cb() 也做了很多工作.

It's doing quite a bit of work in addition to the .sort() call - and this code is just the tip of the iceberg, the helper functions it calls like cb() do a lot of work too.

当您自己直接调用 .sort() 一样容易时，为什么还要这样做?

Why do all that when it's just as easy to call .sort() directly yourself?

此外，需要仔细阅读冗长的 .sortBy() 源代码，以确保它执行的是 numeric 排序而不是字典排序 - 并且 文档没有说！

Also, it takes a close reading of that lengthy .sortBy() source to be sure that it does a numeric sort instead of a lexicographic sort - and the documentation doesn't say!

字典排序(又名字母排序)是将值按字符串排序，而不是按数字排序.例如，它将使用以下顺序:

A lexicographic sort (aka alphabetic sort) is where the values are sorted as strings, not as numbers. So for example it would use this order:

[ 1424, 2367, 241, ... ]

当您自己调用原生数组 .sort() 时，您可以轻松验证它是否使用数字排序:值 b.average - a.average 是总是一个数字.

When you call the native array .sort() yourself, you can easily verify that it uses a numeric sort: the value b.average - a.average is always a number.

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