如何在Javascript中一次性过滤数组元素 [英] How to get filtered in and out elements of array at one go in Javascript

问题描述

我想知道是否存在一种精确的方法来过滤Javascript中未过滤的数组元素，我的意思是，就像一口气.

I wonder if there is a precise way for getting filtered an unfiltered elements of an array in Javascript, I mean, like, in one go.

当前，我使用如下逻辑:

Currently, I use a logic like follows:

const myArray = ['a', 'b', 'c', 'd', 'e']
const filterArray = ['a', 'b']

// I want to combine those two expressions somehow
const filteredInResult = myArray.filter(e => filterArray.includes(e))
const filteredOutResult = myArray.filter(e => !filterArray.includes(e))

console.log(filteredInResult)
console.log(filteredOutResult)

我感觉像解构可能已经有实现的方法了，但是无论如何，我还是想问你们是否有一种方法可以过滤&出一枪.

I felt like a destructuring-like way might already be there to achieve it, but anyway, I prefer asking you guys if there is a way for getting filtered in & out results in one shot.

编辑:如果此问题与此处类似，请继续提醒我但是我在上面的字符串查询中使用了字符串比较和includes，但是过滤表达式可能比这更复杂.因此，我必须强调，问题的重点不在两个字符串数组的区别上.我要再举一个例子，希望问题不会合并:D

SO keeps alerting me if this question is similar to the question here, but I used string comparison and includes for brewity above but the filtering expression may be more complex than that. So, the I must underline that the focus of the question is not on difference of two string arrays. I am leaving another example and hope the questions won't be merged :D

// A more complex use case
const myArray = [
  {id: 1, value: 'a'},
  {id: 2, value: 'b'},
  {id: 3, value: 'c'},
  {id: 4, value: 'd'},
  {id: 5, value: 'e'},
]
const filterArray = ['a', 'b']

// I want to combine those two expressions somehow
const filteredInResult = myArray.filter(e => filterArray.includes(e.value))
const filteredOutResult = myArray.filter(e => !filterArray.includes(e.value))

console.log(filteredInResult)
console.log(filteredOutResult)

推荐答案

如果您担心在myArray上进行两次迭代，则可以 first 考虑降低计算复杂度.因为循环的每次迭代都调用Array.prototype.includes，并且Array.prototype.includes的复杂度为O(n)，所以您的代码的总体复杂度为O(n ^ 2). (外循环:O(n) *内循环:O(n)).因此，请考虑先解决此问题:使用Set和Set.has(一个O(1)操作)，而不要使用数组和.includes.假设您的实际filterArray足够大，以至于需要考虑计算复杂性-设置 do 会产生一些开销.

If you're worried about iterating twice over the myArray, you might first consider reducing the computational complexity. Because each iteration of the loops calls Array.prototype.includes, and the complexity of Array.prototype.includes is O(n), your code has an overall complexity of O(n ^ 2). (outer loop: O(n) * inner loop: O(n)). So, consider fixing that first: use a Set and Set.has, an O(1) operation, instead of an array and .includes. This is assuming that your actual filterArray is large enough that computational complexity is something to worry about - sets do have a bit of an overhead cost.

对于问题的其他(主要)部分，一个选择是在外部创建两个结果数组，然后在迭代时推入相应的结果数组:

As for the other (main) part of the question, one option is to create the two result arrays outside, then push to the appropriate one while iterating:

const myArray = ['a', 'b', 'c', 'd', 'e']
const filterArray = new Set(['a', 'b'])

const filteredInResult = [];
const filteredOutResult = [];
for (const e of myArray) {
  (filterArray.has(e) ? filteredInResult : filteredOutResult).push(e);
}
console.log(filteredInResult)
console.log(filteredOutResult)

也可以使用reduce，尽管我认为它看起来不太好:

Could also use reduce, though I don't think it looks very good:

const myArray = ['a', 'b', 'c', 'd', 'e']
const filterArray = new Set(['a', 'b'])

const { filteredInResult, filteredOutResult } = myArray.reduce((a, e) => {
  a[filterArray.has(e) ? 'filteredInResult' : 'filteredOutResult'].push(e);
  return a;
}, { filteredInResult: [], filteredOutResult: [] });

console.log(filteredInResult)
console.log(filteredOutResult)

这篇关于如何在Javascript中一次性过滤数组元素的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！