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