107 lines
2.2 KiB
Markdown
107 lines
2.2 KiB
Markdown
---
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id: 587d7b89367417b2b2512b4a
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title: 使用解构赋值从嵌套对象中分配变量
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challengeType: 1
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forumTopicId: 301214
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dashedName: use-destructuring-assignment-to-assign-variables-from-nested-objects
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---
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# --description--
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你可以使用前两节课程中相同的原则来解构嵌套对象中的值。
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使用与前面的例子中类似的对象：
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```js
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const user = {
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johnDoe: {
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age: 34,
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email: 'johnDoe@freeCodeCamp.com'
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}
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};
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```
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这是解构对象的属性值赋值给具有相同名字的变量：
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```js
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const { johnDoe: { age, email }} = user;
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```
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这是将对象的属性值赋值给具有不同名字的变量：
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```js
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const { johnDoe: { age: userAge, email: userEmail }} = user;
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```
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# --instructions--
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将两个赋值语句替换成等价的解构赋值。 `lowToday` 和 `highToday` 应该为 `LOCAL_FORECAST` 中 `today.low` 和 `today.high` 的值。
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# --hints--
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不能使用 ES5 的赋值语句。
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```js
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assert(
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!code.match(/lowToday = LOCAL_FORECAST\.today\.low/g) &&
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!code.match(/highToday = LOCAL_FORECAST\.today.high/g)
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);
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```
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应该使用解构创建 `lowToday` 变量。
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```js
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assert(
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code.match(
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/(var|const|let)\s*{\s*today\s*:\s*{\s*(low\s*:\s*lowToday[^}]*|[^,]*,\s*low\s*:\s*lowToday\s*)}\s*}\s*=\s*LOCAL_FORECAST(;|\s+|\/\/)/g
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)
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);
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```
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应该使用解构创建 `highToday` 变量。
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```js
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assert(
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code.match(
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/(var|const|let)\s*{\s*today\s*:\s*{\s*(high\s*:\s*highToday[^}]*|[^,]*,\s*high\s*:\s*highToday\s*)}\s*}\s*=\s*LOCAL_FORECAST(;|\s+|\/\/)/g
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)
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);
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```
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`lowToday` 应等于 `64`，`highToday` 应等于 `77`。
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```js
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assert(lowToday === 64 && highToday === 77);
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```
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# --seed--
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## --seed-contents--
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```js
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const LOCAL_FORECAST = {
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yesterday: { low: 61, high: 75 },
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today: { low: 64, high: 77 },
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tomorrow: { low: 68, high: 80 }
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};
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// Only change code below this line
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const lowToday = LOCAL_FORECAST.today.low;
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const highToday = LOCAL_FORECAST.today.high;
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// Only change code above this line
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```
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# --solutions--
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```js
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const LOCAL_FORECAST = {
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yesterday: { low: 61, high: 75 },
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today: { low: 64, high: 77 },
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tomorrow: { low: 68, high: 80 }
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};
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const { today: { low: lowToday, high: highToday }} = LOCAL_FORECAST;
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```
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