JavaScript 展平嵌套数组 [英] JavaScript flatten nested array

问题描述

我正在尝试将任何长度的嵌套数组展平为单个数组.为什么它显示的是数组而不是数组值?

I am trying to flatten any length of a nested array into a single array. Why it's showing array rather than array value?

function flatten(arr) {
  var res = [];
  for (var i = 0; i < arr.length; i++) {
    if (toString.call(arr[i]) === "[object Array]") {
      res.push(flatten(arr[i]));
    } else {
      res.push(arr[i]);
    }
  }
  return res;
}

console.log(flatten([1, 2, [3, [4, 5, [6]]], 7, 8]));
// [1, 2, Array(2), 7, 8]

推荐答案

你可以用 concat 代替 push 和 reduce 代替 for 循环.

You can use concat instead of push and reduce instead of for loop.

const flatten = data => data.reduce((r, e) => {
  return r = r.concat(Array.isArray(e) ? flatten(e) : e), r
}, [])
 
console.log(flatten([1, 2, [3, [4, 5, [6]]], 7, 8]))

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