116 lines
6.6 KiB
Markdown
116 lines
6.6 KiB
Markdown
---
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id: 587d7b7b367417b2b2512b16
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title: Create complex multi-dimensional arrays
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challengeType: 1
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forumTopicId: 301159
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localeTitle: 创建复杂的多维数组
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---
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## Description
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<section id='description'>
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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<dfn>对象</dfn>(<dfn>Objects</dfn>)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。
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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<dfn>多维(multi-dimensional)</dfn>或嵌套(nested)数组的数据结构。请看如下例子:
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```js
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let nestedArray = [ // 顶层,或第 1 层——最外层的数组
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['deep'], // 数组中的数组,第 2 层
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[
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['deeper'], ['deeper'] // 第 3 层嵌套的两个数组
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],
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[
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[
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['deepest'], ['deepest'] // 第 4 层嵌套的两个数组
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],
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[
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[
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['deepest-est?'] // 第 5 层嵌套的一个数组
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]
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]
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]
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];
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```
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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。
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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:
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```js
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console.log(nestedArray[2][1][0][0][0]);
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// logs: deepest-est?
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```
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既然我们知道数据在哪里,我们就能修改它:
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```js
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nestedArray[2][1][0][0][0] = 'deeper still';
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console.log(nestedArray[2][1][0][0][0]);
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// now logs: deeper still
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```
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</section>
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## Instructions
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<section id='instructions'>
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我们已经定义了一个<code>myNestedArray</code>数组变量。请修改<code>myNestedArray</code>,用<dfn>字符串(string)</dfn>、<dfn>数字(number)</dfn>或者<dfn>布尔值(boolean)</dfn>作为数组的数据元素,使得<code>myNestedArray</code>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<code>'deep'</code>,在第 4 层的数组中包含字符串<code>'deeper'</code>,在第 5 层的数组中包含字符串<code>'deepest'</code>。
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- 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。
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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);'
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- text: <code>myNestedArray</code>应该刚好有 5 层数组嵌套。
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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);'
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- text: <code>myNestedArray</code>里应该有且只有一个字符串<code>"deep"</code>,并且应该出现在第 3 层数组中。
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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);
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- text: <code>myNestedArray</code>里应该有且只有一个字符串<code>"deeper"</code>,并且应该出现在第 4 层数组中。
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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);
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- text: <code>myNestedArray</code>里应该有且只有一个字符串<code>"deepest"</code>,并且应该出现在第 5 层数组中。
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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);
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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let myNestedArray = [
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// change code below this line
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['unshift', false, 1, 2, 3, 'complex', 'nested'],
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['loop', 'shift', 6, 7, 1000, 'method'],
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['concat', false, true, 'spread', 'array'],
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['mutate', 1327.98, 'splice', 'slice', 'push'],
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['iterate', 1.3849, 7, '8.4876', 'arbitrary', 'depth']
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// change code above this line
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];
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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let myNestedArray = [
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// change code below this line
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['unshift', ['deep', ['deeper', ['deepest']]],false, 1, 2, 3, 'complex', 'nested'],
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['loop', 'shift', 6, 7, 1000, 'method'],
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['concat', false, true, 'spread', 'array'],
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['mutate', 1327.98, 'splice', 'slice', 'push'],
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['iterate', 1.3849, 7, '8.4876', 'arbitrary', 'depth']
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// change code above this line
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];
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```
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</section>
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