99 lines
2.3 KiB
Markdown
99 lines
2.3 KiB
Markdown
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---
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id: 567af2437cbaa8c51670a16c
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title: 測試對象的屬性
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challengeType: 1
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videoUrl: 'https://scrimba.com/c/c6Wz4ySr'
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forumTopicId: 18324
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dashedName: testing-objects-for-properties
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---
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# --description--
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有時檢查一個對象屬性是否存在是非常有用的。 我們可以用對象的 `.hasOwnProperty(propname)` 方法來檢查對象是否有指定的屬性。 `.hasOwnProperty()` 找到該屬性時返回 `true`，找不到該屬性時返回 `false`。
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**示例**
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```js
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var myObj = {
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top: "hat",
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bottom: "pants"
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};
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myObj.hasOwnProperty("top");
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myObj.hasOwnProperty("middle");
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```
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第一個 `hasOwnProperty` 返回 `true`，第二個返回 `false`。
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# --instructions--
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修改函數 `checkObj` 檢查 `obj` 是否有 `checkProp` 屬性。 如果屬性存在，返回屬性對應的值。 如果不存在，返回`"Not Found"`。
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# --hints--
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`checkObj({gift: "pony", pet: "kitten", bed: "sleigh"}, "gift")` 應該返回字符串 `pony`。
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```js
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assert(
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checkObj({ gift: 'pony', pet: 'kitten', bed: 'sleigh' }, 'gift') === 'pony'
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);
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```
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`checkObj({gift: "pony", pet: "kitten", bed: "sleigh"}, "pet")` 應該返回字符串 `kitten`。
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```js
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assert(
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checkObj({ gift: 'pony', pet: 'kitten', bed: 'sleigh' }, 'pet') === 'kitten'
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);
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```
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`checkObj({gift: "pony", pet: "kitten", bed: "sleigh"}, "house")` 應該返回字符串 `Not Found`。
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```js
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assert(
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checkObj({ gift: 'pony', pet: 'kitten', bed: 'sleigh' }, 'house') ===
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'Not Found'
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);
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```
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`checkObj({city: "Seattle"}, "city")` 應該返回字符串 `Seattle`。
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```js
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assert(checkObj({ city: 'Seattle' }, 'city') === 'Seattle');
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```
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`checkObj({city: "Seattle"}, "district")` 應該返回字符串 `Not Found`。
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```js
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assert(checkObj({ city: 'Seattle' }, 'district') === 'Not Found');
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```
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`checkObj({pet: "kitten", bed: "sleigh"}, "gift")` 應該返回字符串 `Not Found`。
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```js
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assert(checkObj({ pet: 'kitten', bed: 'sleigh' }, 'gift') === 'Not Found');
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```
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# --seed--
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## --seed-contents--
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```js
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function checkObj(obj, checkProp) {
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// Only change code below this line
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return "Change Me!";
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// Only change code above this line
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}
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```
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# --solutions--
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```js
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function checkObj(obj, checkProp) {
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if(obj.hasOwnProperty(checkProp)) {
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return obj[checkProp];
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} else {
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return "Not Found";
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}
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}
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```
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