2018-10-10 22:03:03 +00:00
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id: 56533eb9ac21ba0edf2244ca
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2021-03-15 03:20:39 +00:00
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title: 使用对象进行查找
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2018-10-10 22:03:03 +00:00
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challengeType: 1
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2020-04-29 10:29:13 +00:00
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videoUrl: 'https://scrimba.com/c/cdBk8sM'
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forumTopicId: 18373
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2021-01-13 02:31:00 +00:00
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dashedName: using-objects-for-lookups
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2018-10-10 22:03:03 +00:00
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---
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2020-12-16 07:37:30 +00:00
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# --description--
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2021-03-15 03:20:39 +00:00
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对象和字典一样,可以用来存储键/值对。 如果数据是扁平的,你可以用对象来查找你想要的值,而不是链式使用 `switch` 或 `if/else` 语句。 当你知道你的输入数据在某个范围时,这种查找方式极为有效。
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2020-12-16 07:37:30 +00:00
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2021-03-15 03:20:39 +00:00
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这是简单的反向字母表:
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2020-04-29 10:29:13 +00:00
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```js
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var alpha = {
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1:"Z",
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2:"Y",
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3:"X",
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4:"W",
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...
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24:"C",
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25:"B",
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26:"A"
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};
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2021-03-15 03:20:39 +00:00
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alpha[2];
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alpha[24];
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2020-04-29 10:29:13 +00:00
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var value = 2;
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2021-03-15 03:20:39 +00:00
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alpha[value];
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2020-04-29 10:29:13 +00:00
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```
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2021-03-15 03:20:39 +00:00
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`alpha[2]` 是字符串 `Y`,`alpha[24]` 是字符串 `C`,`alpha[value]` 是字符串 `Y`。
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2020-12-16 07:37:30 +00:00
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# --instructions--
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2021-03-15 03:20:39 +00:00
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把 switch 语句转化为对象 `lookup` 调用。 使用它来查找 `val` 属性的值,并赋值给 `result` 变量。
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2020-12-16 07:37:30 +00:00
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# --hints--
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2021-03-15 03:20:39 +00:00
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`phoneticLookup("alpha")` 应该等于 `Adams`
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2020-12-16 07:37:30 +00:00
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```js
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assert(phoneticLookup('alpha') === 'Adams');
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```
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2021-03-15 03:20:39 +00:00
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`phoneticLookup("bravo")` 应该等于 `Boston`
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2020-12-16 07:37:30 +00:00
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```js
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assert(phoneticLookup('bravo') === 'Boston');
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```
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2021-03-15 03:20:39 +00:00
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`phoneticLookup("charlie")` 应该等于 `Chicago`
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(phoneticLookup('charlie') === 'Chicago');
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2018-10-10 22:03:03 +00:00
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```
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2021-03-15 03:20:39 +00:00
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`phoneticLookup("delta")` 应该等于 `Denver`
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(phoneticLookup('delta') === 'Denver');
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```
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2018-10-10 22:03:03 +00:00
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2021-03-15 03:20:39 +00:00
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`phoneticLookup("echo")` 应该等于 `Easy`
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2018-10-10 22:03:03 +00:00
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```js
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2020-12-16 07:37:30 +00:00
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assert(phoneticLookup('echo') === 'Easy');
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2018-10-10 22:03:03 +00:00
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```
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2021-03-15 03:20:39 +00:00
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`phoneticLookup("foxtrot")` 应该等于字符串 `Frank`
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(phoneticLookup('foxtrot') === 'Frank');
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```
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2018-10-10 22:03:03 +00:00
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2021-03-15 03:20:39 +00:00
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`phoneticLookup("")` 应该等于 `undefined`。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(typeof phoneticLookup('') === 'undefined');
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```
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2021-03-15 03:20:39 +00:00
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请不要修改 `return` 语句
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(code.match(/return\sresult;/));
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```
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2018-10-10 22:03:03 +00:00
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2021-03-15 03:20:39 +00:00
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请不要使用 `case`、`switch`、`if` 语句
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2020-04-29 10:29:13 +00:00
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2018-10-10 22:03:03 +00:00
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```js
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2020-12-16 07:37:30 +00:00
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assert(
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!/case|switch|if/g.test(code.replace(/([/]{2}.*)|([/][*][^/*]*[*][/])/g, ''))
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);
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2018-10-10 22:03:03 +00:00
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```
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2020-04-29 10:29:13 +00:00
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2021-01-13 02:31:00 +00:00
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# --seed--
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## --seed-contents--
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```js
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// Setup
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function phoneticLookup(val) {
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var result = "";
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// Only change code below this line
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switch(val) {
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case "alpha":
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result = "Adams";
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break;
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case "bravo":
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result = "Boston";
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break;
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case "charlie":
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result = "Chicago";
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break;
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case "delta":
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result = "Denver";
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break;
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case "echo":
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result = "Easy";
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break;
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case "foxtrot":
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result = "Frank";
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}
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// Only change code above this line
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return result;
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}
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phoneticLookup("charlie");
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```
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2020-12-16 07:37:30 +00:00
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# --solutions--
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2021-01-13 02:31:00 +00:00
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```js
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function phoneticLookup(val) {
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var result = "";
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var lookup = {
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alpha: "Adams",
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bravo: "Boston",
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charlie: "Chicago",
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delta: "Denver",
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echo: "Easy",
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foxtrot: "Frank"
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};
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result = lookup[val];
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return result;
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}
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```
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