94 lines
1.2 KiB
Markdown
94 lines
1.2 KiB
Markdown
---
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id: 56533eb9ac21ba0edf2244b0
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title: 複合賦值之 -=
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challengeType: 1
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videoUrl: 'https://scrimba.com/c/c2Qv7AV'
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forumTopicId: 16660
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dashedName: compound-assignment-with-augmented-subtraction
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---
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# --description--
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與 `+=` 操作符類似，`-=` 操作符用來對一個變量進行減法賦值操作。
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```js
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myVar = myVar - 5;
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```
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將從 `myVar` 中減去 `5`。 等價於：
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```js
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myVar -= 5;
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```
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# --instructions--
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使用 `-=` 操作符對 `a`、`b` 和 `c` 實現相減賦值操作。
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# --hints--
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`a` 應該等於 `5`。
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```js
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assert(a === 5);
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```
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`b` 應該等於 `-6`。
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```js
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assert(b === -6);
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```
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`c` 應該等於 `2`。
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```js
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assert(c === 2);
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```
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應該對每個變量使用 `-=` 操作符。
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```js
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assert(code.match(/-=/g).length === 3);
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```
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不要修改註釋上面的代碼。
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```js
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assert(
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/let a = 11;/.test(code) && /let b = 9;/.test(code) && /let c = 3;/.test(code)
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);
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```
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# --seed--
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## --after-user-code--
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```js
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(function(a,b,c){ return "a = " + a + ", b = " + b + ", c = " + c; })(a,b,c);
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```
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## --seed-contents--
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```js
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let a = 11;
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let b = 9;
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let c = 3;
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// Only change code below this line
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a = a - 6;
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b = b - 15;
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c = c - 1;
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```
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# --solutions--
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```js
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let a = 11;
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let b = 9;
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let c = 3;
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a -= 6;
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b -= 15;
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c -= 1;
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```
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