Introduction to JavaScript destructuring assignment

Introduction to JavaScript destructuring assignment

JavaScript destructuring assignment is a syntax that simplifies variable assignment, allowing data to be extracted from an array or object and assigned to a variable. 【https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment】

1. Array destructuring and assignment

let  numbers = [1, 2, 3];
let  [a, b, c] = numbers;
console.log(b); // 输出: 2
console.log(a, b, c); // 输出: 1 2 3

2. Object destructuring and assignment

let person = {
  name: 'Alice',
  age: 25,
  gender: 'female'
};
let { name, age, gender } = person;
console.log(name, age, gender); //  输出: Alice 25 female

3. When destructuring and assigning values, you can also set default values ​​for variables. You can deal with non-existent variables by specifying default values.

let arr = [1, 2];
let [x, y, z = 3] = arr;
console.log(x, y, z); // 输出: 1 2 3

4. JavaScript’s destructuring assignment can be used not only for simple arrays and objects, but also for destructuring nested structures, function parameters, and return values.
☆ Destructuring assignment of nested structures:

let nestedObj = {  
  outer: {  
    inner: {  
      value: 42  
    }  
  }  
};
let { outer: { inner: { value } } } = nestedObj;  
console.log(value); // 输出 42  

☆ Destructuring assignment of function parameters:

function greet({ name, age }) {  
  console.log(`Hello, my name is ${name} and I am ${age} years old.`);  
}
greet({ name: "Alice", age: 30 }); // 输出 "Hello, my name is Alice and I am 30 years old."  

☆ Destructuring assignment of function return value:

function getFullName({ firstName, lastName }) {  
  return {  
    fullName: `${firstName} ${lastName}`  
  };  
}
const { fullName } = getFullName({ firstName: "John", lastName: "Doe" });  
console.log(fullName); // 输出 "John Doe"