2021-05-05 17:13:49 +00:00
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---
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id: 56533eb9ac21ba0edf2244d8
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title: 邏輯與運算符
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challengeType: 1
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videoUrl: 'https://scrimba.com/c/cvbRVtr'
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forumTopicId: 16799
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dashedName: comparisons-with-the-logical-and-operator
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---
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# --description--
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2021-06-14 14:47:03 +00:00
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有時你需要在一次判斷中做多個操作。 當且僅當<dfn>運算符</dfn>的左邊和右邊都是 true,<dfn>邏輯與</dfn>運算符(`&&`)纔會返回 `true`。
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2021-05-05 17:13:49 +00:00
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同樣的效果可以通過 if 語句的嵌套來實現:
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```js
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if (num > 5) {
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if (num < 10) {
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return "Yes";
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}
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}
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return "No";
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```
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只有當 `num` 的值大於 `5` 並且小於`10` 時纔會返回 `Yes`。 相同的邏輯可被寫爲:
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```js
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if (num > 5 && num < 10) {
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return "Yes";
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}
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return "No";
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```
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# --instructions--
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2021-06-14 14:47:03 +00:00
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請使用 `&&` 運算符把兩個 if 語句合併爲一個 if 語句,如果 `val` 小於或等於 `50` 並且大於或等於 `25` 時,返回 `Yes`。 否則,將返回 `No`。
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2021-05-05 17:13:49 +00:00
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# --hints--
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你應該使用 `&&` 運算符一次。
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```js
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assert(code.match(/&&/g).length === 1);
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```
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你應該只有一個 `if` 表達式。
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```js
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assert(code.match(/if/g).length === 1);
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```
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`testLogicalAnd(0)` 應該返回字符串 `No`
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```js
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assert(testLogicalAnd(0) === 'No');
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```
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`testLogicalAnd(24)` 應該返回字符串 `No`
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```js
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assert(testLogicalAnd(24) === 'No');
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```
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`testLogicalAnd(25)` 應該返回字符串 `Yes`
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```js
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assert(testLogicalAnd(25) === 'Yes');
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```
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`testLogicalAnd(30)` 應該返回字符串 `Yes`
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```js
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assert(testLogicalAnd(30) === 'Yes');
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```
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`testLogicalAnd(50)` 應該返回字符串 `Yes`
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```js
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assert(testLogicalAnd(50) === 'Yes');
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```
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`testLogicalAnd(51)` 應該返回字符串 `No`
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```js
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assert(testLogicalAnd(51) === 'No');
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```
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`testLogicalAnd(75)` 應該返回字符串 `No`
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```js
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assert(testLogicalAnd(75) === 'No');
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```
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`testLogicalAnd(80)` 應該返回字符串 `No`
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```js
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assert(testLogicalAnd(80) === 'No');
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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 testLogicalAnd(val) {
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// Only change code below this line
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if (val) {
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if (val) {
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return "Yes";
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}
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}
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// Only change code above this line
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return "No";
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}
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testLogicalAnd(10);
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```
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# --solutions--
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```js
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function testLogicalAnd(val) {
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if (val >= 25 && val <= 50) {
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return "Yes";
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}
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return "No";
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}
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```
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