英文:
What is an example of "array destructuring" via "assignment pattern" in JavaScript?
问题
Here is the translation of the content you provided:
这个MDN关于解构赋值的文档说:“对于对象和数组的解构,有两种解构模式:绑定模式和赋值模式”。因此,应该有四种解构语法:
- 类型1:通过绑定模式进行对象解构
- 类型2:通过绑定模式进行数组解构
- 类型3:通过赋值模式进行对象解构
- 类型4:通过赋值模式进行数组解构
我已经多次阅读了MDN文档页面,但该页面似乎只提供了前三种类型的示例。谷歌搜索似乎也没有帮助。
Type 4的示例是什么呢?
更新1:
对于Type 3,MDN提供了以下示例:
// 这将把 a 赋值给 numbers[0],将 b 赋值给 number[1]
({ a: numbers[0], b: numbers[1] } = obj);
Type 4的等效示例是什么呢?谢谢!
英文:
This MDN documentation on destructuring assignment says that "for both object and array destructuring, there are two kinds of destructuring patterns: binding pattern and assignment pattern". Therefore, there should be four types of destructuring syntax:
- Type 1: object destructuring via binding pattern
- Type 2: array destructuring via binding pattern
- Type 3: object destructuring via assignment pattern
- Type 4: array destructuring via assignment pattern
I have read through the MDN documentation page many times, and the page seems to have provided examples only for the first 3 types. Googling doesn't seem to help either.
What would be an example of Type 4?
Thanks!
Update 1:
For Type 3, MDN provided this example:
// This assigns a to numbers[0] , and b to number[1]
({ a: numbers[0], b: numbers[1] } = obj);
What would be an equivalent example for Type 4? Thanks!
答案1
得分: 0
以下是您列出的四种类型的示例:
-
类型1:通过绑定模式进行对象解构
const person = { name: 'Alice', age: 30, }; const { name, age } = person;
-
类型2:通过绑定模式进行数组解构
const rgb = [255, 200, 100]; const [red, green, blue] = rgb;
-
类型3:通过赋值模式进行对象解构
const person = { name: 'Bob', age: 25, }; let name, age; ({ name, age } = person);
-
类型4:通过赋值模式进行数组解构
const rgb = [255, 200, 100]; let red, green, blue; [red, green, blue] = rgb;
-
类型4的高级示例:
const obj = { numbers: [1, 2, 3, 4, 5], }; let a, b; // 这将a赋值为obj.numbers[0],将b赋值为obj.numbers[1] [a, b] = obj.numbers;
要使用赋值模式和数组解构来分别提取数组值的每个索引元素,请执行以下操作:
const obj = {
numbers: [1, 2, 3, 4, 5],
};
let a, c, e;
// 这将obj.numbers[0]赋值给a,obj.numbers[2]赋值给c,obj.numbers[4]赋值给e
([a, , c, , e] = obj.numbers);
在此示例中,我们正在从obj
对象中解构numbers
数组,并将其第1、第3和第5个元素分别分配给变量a
、c
和e
。我们使用逗号之间的省略来跳过我们不想提取的元素。
英文:
Here are examples of each of the four types you listed:
-
Type 1: Object destructuring via binding pattern
const person = { name: 'Alice', age: 30, }; const { name, age } = person;
-
Type 2: Array destructuring via binding pattern
const rgb = [255, 200, 100]; const [red, green, blue] = rgb;
-
Type 3: Object destructuring via assignment pattern
const person = { name: 'Bob', age: 25, }; let name, age; ({ name, age } = person);
-
Type 4: Array destructuring via assignment pattern
const rgb = [255, 200, 100]; let red, green, blue; [red, green, blue] = rgb;
-
Advanced example for type 4:
const obj = { numbers: [1, 2, 3, 4, 5], }; let a, b; // This assigns a to obj.numbers[0], and b to obj.numbers[1] [a, b] = obj.numbers;
To surgically and individually extract each indexed element of an array value using array destructuring with the assignment pattern, do the following:
const obj = {
numbers: [1, 2, 3, 4, 5],
};
let a, c, e;
// This assigns obj.numbers[0] to a, obj.numbers[2] to c, and obj.numbers[4] to c
([a, , c, , e] = obj.numbers);
In this example, we're destructuring the numbers
array from the obj
object and assigning its 1st, 3rd, and 5th elements to the variables a
, c
, and e
respectively. We use elisions between the commas to skip the elements we don't want to extract.
答案2
得分: 0
MDN 应该用一个更清晰和简单的示例来解释类型 4。这里是示例:
const source = [1, 2, 3];
const target = [4, 5];
[target[0], target[1]] = source; // target = [1, 2]
此外,JavaScript 数组只是具有索引属性的对象,因此上面的代码也可以写成以下类型 3 格式:
({ 0: target[0], 1: target[1] } = source);
英文:
MDN should have explained Type 4 with a clearer and simpler example. Here you go:
const source = [1, 2, 3];
const target = [4, 5];
[target[0], target[1]] = source; // target = [1, 2]
Also, JavaScript arrays are just objects with indexed properties, so the above can also be written as the Type 3 format below:
({ 0: target[0], 1: target[1] } = source);
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