javascript - lodash - 如果所有值都为空，则从数据表(二维矩阵)中删除列

Question

我有一个像这样的二维矩阵，其中第一行是列名，其他行是值。

var datatable = [
  ["a", "b",   "c",   "d"],  //first row are columns names
  [ 1,   0,     null,  3 ],  //other rows are values
  [ 6,   null,  null,  8 ]
];

我想在所有值都为 null 时删除列，如下所示:

var datatable = [
  ["a", "b",   "d"],  //first row are columns names
  [ 1,   0,     3 ],  //other rows are values
  [ 6,   null,  8 ]
];

行数和列数可以变化。如果有一种紧凑而快速的方法可以使用 lodash 实现它，那就太完美了。

Answer 1

使用 .flow() 创建一个使用 _.unzip() 转置数组的函数，拒绝所有 null 的数组值，然后将数组解压缩回原始形式:

const { flow, partialRight: pr, unzip, reject, tail, every, isNull } = _; // convert to imports

const fn = flow(
  unzip,
  pr(reject, flow(tail, pr(every, isNull))),
  unzip,
);

const datatable = [
  ["a", "b",   "c",   "d"],  //first row are columns names
  [ 1,   0,     null,  3 ],  //other rows are values
  [ 6,   null,  null,  8 ]
];

const result = fn(datatable);

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

还有更简洁的 lodash/fp 解决方案:

const { flow, unzip, reject, tail, every, isNull } = _; // convert to imports

const fn = flow(
  unzip,
  reject(flow(
    tail,
    every(isNull)
  )),
  unzip,
);

const datatable = [
  ["a", "b",   "c",   "d"],  //first row are columns names
  [ 1,   0,     null,  3 ],  //other rows are values
  [ 6,   null,  null,  8 ]
];

const result = fn(datatable);

console.log(result);

<script src='https://cdn.jsdelivr.net/g/lodash@4(lodash.min.js+lodash.fp.min.js)'></script>