67 lines
4.4 KiB
Markdown
67 lines
4.4 KiB
Markdown
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---
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id: 8d5823c8c441eddfaeb5bdef
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title: Create a Map Data Structure
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challengeType: 1
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videoUrl: ''
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localeTitle: 创建地图数据结构
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---
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## Description
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<section id="description">接下来的几个挑战将涵盖地图和哈希表。映射是存储键值对的数据结构。在JavaScript中，我们可以将它们作为对象使用。地图可根据键值快速查找存储的项目，是非常常见且有用的数据结构。说明：让我们开始创建自己的地图。因为JavaScript对象提供了比我们在此处编写的任何内容更有效的地图结构，所以这主要是作为学习练习。但是，JavaScript对象仅向我们提供某些操作。如果我们想定义自定义操作怎么办？使用此处提供的<code>Map</code>对象作为JavaScript <code>object</code>的包装器。在Map对象上创建以下方法和操作： <ul><li> <code>add</code>接受要添加到地图的<code>key, value</code>对。 </li><li> <code>remove</code>接受一个键并删除关联的<code>key, value</code>对</li><li> <code>get</code>接受一个<code>key</code>并返回存储的<code>value</code> </li><li>如果密钥存在<code>has</code>接受<code>key</code>并返回<dfn>true，</dfn>否则返回<dfn>false</dfn> 。 </li><li> <code>values</code>返回地图中所有<code>values</code>的数组</li><li> <code>size</code>返回地图中的项目数</li><li> <code>clear</code>清空地图</li></ul></section>
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## Instructions
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<section id="instructions">
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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: 存在地图数据结构。
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testString: 'assert((function() { var test = false; if (typeof Map !== "undefined") { test = new Map() }; return (typeof test == "object")})(), "The Map data structure exists.");'
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- text: Map对象具有以下方法：add，remove，get，has，values，clear和size。
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testString: 'assert((function() { var test = false; if (typeof Map !== "undefined") { test = new Map() }; return (typeof test.add == "function" && typeof test.remove == "function" && typeof test.get == "function" && typeof test.has == "function" && typeof test.values == "function" && typeof test.clear == "function" && typeof test.size == "function")})(), "The Map object has the following methods: add, remove, get, has, values, clear, and size.");'
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- text: add方法将项添加到地图中。
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testString: 'assert((function() { var test = false; if (typeof Map !== "undefined") { test = new Map() }; test.add(5,6); test.add(2,3); test.add(2,5); return (test.size() == 2)})(), "The add method adds items to the map.");'
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- text: has方法对于添加的项返回true，对于缺少的项返回false。
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testString: 'assert((function() { var test = false; if (typeof Map !== "undefined") { test = new Map() }; test.add("test","value"); return (test.has("test") && !test.has("false"))})(), "The has method returns true for added items and false for absent items.");'
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- text: get方法接受键作为输入并返回关联的值。
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testString: 'assert((function() { var test = false; if (typeof Map !== "undefined") { test = new Map() }; test.add("abc","def"); return (test.get("abc") == "def")})(), "The get method accepts keys as input and returns the associated values.");'
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- text: values方法将存储在映射中的所有值作为数组中的字符串返回。
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testString: 'assert((function() { var test = false; if (typeof Map !== "undefined") { test = new Map() }; test.add("a","b"); test.add("c","d"); test.add("e","f"); var vals = test.values(); return (vals.indexOf("b") != -1 && vals.indexOf("d") != -1 && vals.indexOf("f") != -1)})(), "The values method returns all the values stored in the map as strings in an array.");'
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- text: clear方法清空映射，size方法返回映射中存在的项目数。
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testString: 'assert((function() { var test = false; if (typeof Map !== "undefined") { test = new Map() }; test.add("b","b"); test.add("c","d"); test.remove("asdfas"); var init = test.size(); test.clear(); return (init == 2 && test.size() == 0)})(), "The clear method empties the map and the size method returns the number of items present in the map.");'
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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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var Map = function() {
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this.collection = {};
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// change code below this line
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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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// solution required
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```
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</section>
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