2021-05-05 10:13:49 -07:00
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---
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id: 56533eb9ac21ba0edf2244ca
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title: 使用對象進行查找
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challengeType: 1
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videoUrl: 'https://scrimba.com/c/cdBk8sM'
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forumTopicId: 18373
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dashedName: using-objects-for-lookups
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---
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# --description--
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對象和字典一樣,可以用來存儲鍵/值對。 如果數據是扁平的,你可以用對象來查找你想要的值,而不是鏈式使用 `switch` 或 `if/else` 語句。 當你知道你的輸入數據在某個範圍時,這種查找方式極爲有效。
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這是簡單的反向字母表:
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```js
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2021-10-27 15:10:57 +00:00
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const 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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2021-10-27 15:10:57 +00:00
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2021-05-05 10:13:49 -07:00
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alpha[2];
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alpha[24];
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2021-10-27 15:10:57 +00:00
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const value = 2;
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2021-05-05 10:13:49 -07:00
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alpha[value];
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```
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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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# --instructions--
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把 switch 語句轉化爲對象 `lookup` 調用。 使用它來查找 `val` 屬性的值,並賦值給 `result` 變量。
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# --hints--
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`phoneticLookup("alpha")` 應該等於 `Adams`
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```js
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assert(phoneticLookup('alpha') === 'Adams');
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```
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`phoneticLookup("bravo")` 應該等於 `Boston`
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```js
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assert(phoneticLookup('bravo') === 'Boston');
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```
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`phoneticLookup("charlie")` 應該等於 `Chicago`
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```js
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assert(phoneticLookup('charlie') === 'Chicago');
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```
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`phoneticLookup("delta")` 應該等於 `Denver`
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```js
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assert(phoneticLookup('delta') === 'Denver');
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```
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`phoneticLookup("echo")` 應該等於 `Easy`
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```js
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assert(phoneticLookup('echo') === 'Easy');
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```
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`phoneticLookup("foxtrot")` 應該等於字符串 `Frank`
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```js
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assert(phoneticLookup('foxtrot') === 'Frank');
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```
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`phoneticLookup("")` 應該等於 `undefined`。
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```js
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assert(typeof phoneticLookup('') === 'undefined');
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```
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請不要修改 `return` 語句
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```js
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assert(code.match(/return\sresult;/));
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```
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請不要使用 `case`、`switch`、`if` 語句
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```js
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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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```
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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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let 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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# --solutions--
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```js
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function phoneticLookup(val) {
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2021-10-27 15:10:57 +00:00
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let result = "";
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2021-05-05 10:13:49 -07:00
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2021-10-27 15:10:57 +00:00
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const lookup = {
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2021-05-05 10:13:49 -07:00
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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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