freeCodeCamp/create-complex-multi-dimensional-arrays.md at dec409a4bd667e4979305cc1e86e0702bbc2c707

Oliver Eyton-Williams dec409a4bd fix: s/localeTitle/title/g

2020-10-06 23:10:08 +05:30

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id, challengeType, forumTopicId, title

id	challengeType	forumTopicId	title
587d7b7b367417b2b2512b16	1	301159	创建复杂的多维数组

Description

很好！你已经学到很多关于数组的知识了！但这些只是一个开始，你将在接下来的小节中学习到与数组相关的更多知识。但在继续去学习对象（Objects）之前，让我们再花一点时间看一看，数组怎样能够变得比之前的挑战中更复杂一点。数组的一个强大的特性是，它可以包含其他数组，甚至完全由其他数组组成。我们已经在上一个挑战中看到了包含数组的数组，但它还算是比较简单的。数组中的数组还可以在包含其他数组，数组中是可以嵌套任意层的数组的。数组从而可以被用来实现非常复杂的叫做多维（multi-dimensional）或嵌套（nested）数组的数据结构。请看如下例子：

let nestedArray = [ // 顶层，或第 1 层——最外层的数组
  ['deep'], // 数组中的数组，第 2 层
  [
    ['deeper'], ['deeper'] // 第 3 层嵌套的两个数组
  ],
  [
    [
      ['deepest'], ['deepest'] // 第 4 层嵌套的两个数组
    ],
    [
      [
        ['deepest-est?'] // 第 5 层嵌套的一个数组
      ]
    ]
  ]
];

虽然这个例子看起来错综复杂，但这样复杂的数组并不算罕见，尤其是在处理大量数据的时候。但我们仍能简单地用方括号符号来访问到嵌套得最深的数组：

console.log(nestedArray[2][1][0][0][0]);
// logs: deepest-est?

既然我们知道数据在哪里，我们就能修改它：

nestedArray[2][1][0][0][0] = 'deeper still';

console.log(nestedArray[2][1][0][0][0]);
// now logs: deeper still

Instructions

我们已经定义了一个myNestedArray数组变量。请修改myNestedArray，用字符串（string）、数字（number）或者布尔值（boolean）作为数组的数据元素，使得myNestedArray刚好有 5 层数组嵌套（记住，最外层的数组是第 1 层）。请在第 3 层的数组中包含字符串'deep'，在第 4 层的数组中包含字符串'deeper'，在第 5 层的数组中包含字符串'deepest'。

Tests

tests:
  - text: <code>myNestedArray</code>中的数据元素应当只能是字符串、数字或者布尔值。
    testString: 'assert.strictEqual((function(arr) { let flattened = (function flatten(arr) { const flat = [].concat(...arr); return flat.some (Array.isArray) ? flatten(flat) : flat; })(arr); for (let i = 0; i < flattened.length; i++) { if ( typeof flattened[i] !== ''number'' && typeof flattened[i] !== ''string'' && typeof flattened[i] !== ''boolean'') { return false } } return true })(myNestedArray), true);'
  - text: <code>myNestedArray</code>应该刚好有 5 层数组嵌套。
    testString: 'assert.strictEqual((function(arr) {let depth = 0;function arrayDepth(array, i, d) { if (Array.isArray(array[i])) {  arrayDepth(array[i], 0, d + 1);} else {  depth = (d > depth) ? d : depth;}if (i < array.length) {  arrayDepth(array, i + 1, d);}  }arrayDepth(arr, 0, 0);return depth;})(myNestedArray), 4);'
  - text: <code>myNestedArray</code>里应该有且只有一个字符串<code>&quot;deep&quot;</code>，并且应该出现在第 3 层数组中。
    testString: assert((function howDeep(array, target, depth = 0) {return array.reduce((combined, current) => {if (Array.isArray(current)) {  return combined.concat(howDeep(current, target, depth + 1));} else if (current === target) {  return combined.concat(depth);} else {  return combined;}}, []);})(myNestedArray, 'deep').length === 1 && (function howDeep(array, target, depth = 0) {return array.reduce((combined, current) => {if (Array.isArray(current)) {  return combined.concat(howDeep(current, target, depth + 1));} else if (current === target) {  return combined.concat(depth);} else {  return combined;}}, []);})(myNestedArray, 'deep')[0] === 2);
  - text: <code>myNestedArray</code>里应该有且只有一个字符串<code>&quot;deeper&quot;</code>，并且应该出现在第 4 层数组中。
    testString: assert((function howDeep(array, target, depth = 0) {return array.reduce((combined, current) => {if (Array.isArray(current)) {  return combined.concat(howDeep(current, target, depth + 1));} else if (current === target) {  return combined.concat(depth);} else {  return combined;}}, []);})(myNestedArray, 'deeper').length === 1 && (function howDeep(array, target, depth = 0) {return array.reduce((combined, current) => {if (Array.isArray(current)) {  return combined.concat(howDeep(current, target, depth + 1));} else if (current === target) {  return combined.concat(depth);} else {  return combined;}}, []);})(myNestedArray, 'deeper')[0] === 3);
  - text: <code>myNestedArray</code>里应该有且只有一个字符串<code>&quot;deepest&quot;</code>，并且应该出现在第 5 层数组中。
    testString: assert((function howDeep(array, target, depth = 0) {return array.reduce((combined, current) => {if (Array.isArray(current)) {  return combined.concat(howDeep(current, target, depth + 1));} else if (current === target) {  return combined.concat(depth);} else {  return combined;}}, []);})(myNestedArray, 'deepest').length === 1 && (function howDeep(array, target, depth = 0) {return array.reduce((combined, current) => {if (Array.isArray(current)) {  return combined.concat(howDeep(current, target, depth + 1));} else if (current === target) {  return combined.concat(depth);} else {  return combined;}}, []);})(myNestedArray, 'deepest')[0] === 4);

Challenge Seed

let myNestedArray = [
  // change code below this line
  ['unshift', false, 1, 2, 3, 'complex', 'nested'],
  ['loop', 'shift', 6, 7, 1000, 'method'],
  ['concat', false, true, 'spread', 'array'],
  ['mutate', 1327.98, 'splice', 'slice', 'push'],
  ['iterate', 1.3849, 7, '8.4876', 'arbitrary', 'depth']
  // change code above this line
];

Solution

let myNestedArray = [
  // change code below this line
  ['unshift', ['deep', ['deeper', ['deepest']]],false, 1, 2, 3, 'complex', 'nested'],
  ['loop', 'shift', 6, 7, 1000, 'method'],
  ['concat', false, true, 'spread', 'array'],
  ['mutate', 1327.98, 'splice', 'slice', 'push'],
  ['iterate', 1.3849, 7, '8.4876', 'arbitrary', 'depth']
  // change code above this line
];

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