在 .map 内排序会影响原始数组，而不是返回新数组

Question

我有一个二维数字数组：array1。我想映射 array1 中的每个数组并对每个数组中的数字进行排序并将它们返回到一个新数组：sortedRows。我知道对数组进行映射会返回一个新数组，但是当我在映射过程中对每个内部数组进行排序时，它会对 array1 中的所有数字以及 sortedRows 进行排序。

我已经尝试将 array1 单独映射到行，然后映射/排序到 sortedRows，并且我尝试使用扩展运算符 (rows = [...array1]) 进行复制。两种尝试都在下面得到相同的结果。

let array1 = [[5, 3, 4, 6, 7, 8, 9, 1, 2], 
             [6, 7, 2, 1, 9, 5, 3, 4, 8],
             [1, 9, 8, 3, 4, 2, 5, 6, 7],
             [8, 5, 9, 7, 6, 1, 4, 2, 3],
             [4, 2, 6, 8, 5, 3, 7, 9, 1],
             [7, 1, 3, 9, 2, 4, 8, 5, 6],
             [9, 6, 1, 5, 3, 7, 2, 8, 4],
             [2, 8, 7, 4, 1, 9, 6, 3, 5],
             [3, 4, 5, 2, 8, 6, 1, 7, 9]]

let sortedRows = array1.map(arr => arr.sort((a, b) => a - b))

console.log(array1)
console.log(sortedRows)
// expected

[ [5, 3, 4, 6, 7, 8, 9, 1, 2], 
  [6, 7, 2, 1, 9, 5, 3, 4, 8],
  [1, 9, 8, 3, 4, 2, 5, 6, 7],
  [8, 5, 9, 7, 6, 1, 4, 2, 3],
  [4, 2, 6, 8, 5, 3, 7, 9, 1],
  [7, 1, 3, 9, 2, 4, 8, 5, 6],
  [9, 6, 1, 5, 3, 7, 2, 8, 4],
  [2, 8, 7, 4, 1, 9, 6, 3, 5],
  [3, 4, 5, 2, 8, 6, 1, 7, 9]]
[ [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ] ]


//actual

[ [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ] ]
[ [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],
  [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ] ]

Answer 1

.sort 改变原始数组，所以当你有

array1.map(arr =>

那里的arr 指的是现有的子数组 - 如果您在其上调用.sort，您将更改该子数组。

改为先复制数组：

const sortedRows = array1.map(arr => arr.slice().sort((a, b) => a - b))

let array1 = [[5, 3, 4, 6, 7, 8, 9, 1, 2], 
             [6, 7, 2, 1, 9, 5, 3, 4, 8],
             [1, 9, 8, 3, 4, 2, 5, 6, 7],
             [8, 5, 9, 7, 6, 1, 4, 2, 3],
             [4, 2, 6, 8, 5, 3, 7, 9, 1],
             [7, 1, 3, 9, 2, 4, 8, 5, 6],
             [9, 6, 1, 5, 3, 7, 2, 8, 4],
             [2, 8, 7, 4, 1, 9, 6, 3, 5],
             [3, 4, 5, 2, 8, 6, 1, 7, 9]];

const sortedRows = array1.map(arr => arr.slice().sort((a, b) => a - b));

document.write(array1.join('<br>'));
document.write('<br><br><br>' + sortedRows.join('<br>'));