Javascript/lodash 如何删除空数组答案

【问题标题】：Javascript/lodash how to remove empty arraysJavascript/lodash 如何删除空数组
【发布时间】：2017-06-17 08:59:27
【问题描述】：

我正在使用这种结构：

[
   [
      {
         "comments":"asd",
         "movement":"Back Squat",
         "userID":"wDHZv3OL55SIymHkhMUejNleNkx1",
         "weight":"330"
      }
   ],
   [
      {
         "comments":"asd",
         "movement":"Bench Press",
         "userID":"wDHZv3OL55SIymHkhMUejNleNkx1",
         "weight":"100"
      }
   ],
   [
      {
         "comments":"Comment",
         "movement":"Clean",
         "userID":"wDHZv3OL55SIymHkhMUejNleNkx1",
         "weight":"195"
      }
   ],
   [

   ],
   [

   ],
   [
      {
         "comments":"Front squat comment alpha",
         "movement":"Front Squat",
         "userID":"wDHZv3OL55SIymHkhMUejNleNkx1",
         "weight":"315"
      }
   ],
   [

   ],
   [

   ],
   [

   ],
   [

   ],
   [

   ],
   [
      {
         "comments":"abc",
         "movement":"Strict Press",
         "userID":"wDHZv3OL55SIymHkhMUejNleNkx1",
         "weight":"155"
      }
   ]
]

这是我以 JSON 格式使用的输入。可以看到有多个空数组。

我将如何过滤这些数组并删除空数组？

【问题讨论】：

"This structure"：对于单个结构，这不是有效的 JavaScript 表示法。你能用 JavaScript 表示法提供输入和所需的输出吗？
我已经添加了输入
提供的答案将完成这项工作。您声称他们返回一个空数组的说法很奇怪。如果那真的是 JSON（即文本格式），那么你当然首先需要将它解析成一个真正的数组。

标签： javascript lodash

【解决方案1】：

使用原生的Array#filter或lodash的_.filter()，保留长度不为0的子数组。

Array#filter

var arrs = [[{"comments":"asd","movement":"Back Squat","userID":"wDHZv3OL55SIymHkhMUejNleNkx1","weight":"330"}],[{"comments":"asd","movement":"Bench Press","userID":"wDHZv3OL55SIymHkhMUejNleNkx1","weight":"100"}],[{"comments":"Comment","movement":"Clean","userID":"wDHZv3OL55SIymHkhMUejNleNkx1","weight":"195"}],[],[],[{"comments":"Front squat comment alpha","movement":"Front Squat","userID":"wDHZv3OL55SIymHkhMUejNleNkx1","weight":"315"}],[],[],[],[],[],[{"comments":"abc","movement":"Strict Press","userID":"wDHZv3OL55SIymHkhMUejNleNkx1","weight":"155"}]];

var result = arrs.filter(function(sub) {
  return sub.length;
});

console.log(result);

Lodash 的 _.filter() 和 _.size：

var arrs = [[{"comments":"asd","movement":"Back Squat","userID":"wDHZv3OL55SIymHkhMUejNleNkx1","weight":"330"}],[{"comments":"asd","movement":"Bench Press","userID":"wDHZv3OL55SIymHkhMUejNleNkx1","weight":"100"}],[{"comments":"Comment","movement":"Clean","userID":"wDHZv3OL55SIymHkhMUejNleNkx1","weight":"195"}],[],[],[{"comments":"Front squat comment alpha","movement":"Front Squat","userID":"wDHZv3OL55SIymHkhMUejNleNkx1","weight":"315"}],[],[],[],[],[],[{"comments":"abc","movement":"Strict Press","userID":"wDHZv3OL55SIymHkhMUejNleNkx1","weight":"155"}]];

var result = _.filter(arrs, _.size);

console.log(result);

&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"&gt;&lt;/script&gt;

【讨论】：

【解决方案2】：

如果顶级数组中的所有项目都是数组，那么您可以使用 isEmpty 谓词来 lodash 的 reject。

let result = _.reject(data, _.isEmpty);

isEmpty 也将为空对象返回 true，因此如果您的顶级数组可以包含此类项目，那么只需删除空数组，您可以编写一个新函数来仅返回空数组并将其用作谓词拒绝：

let isEmptyArray = item => _.isArray(item) && _.isEmpty(item);

let result = _.reject(data, isEmptyArray);

【讨论】：

【解决方案3】：

依次测试每个数组，看它是否具有非零（真实）长度。如果是，请将其放入您的新数组中。

var array_of_arrays = [[1], [1,1], [], [], [1]];
var array_of_non_empty_arrays = array_of_arrays.filter((array) => array.length);
console.log(array_of_non_empty_arrays);

【讨论】：

这将返回一个空数组作为结果。
你可以使用解构来缩短它一点filter(({ length }) => length)
@JoeBerthelot — 它不在答案中嵌入的现场演示中。由于您未能在问题中提供minimal reproducible example，因此我不得不自己构建输入。