Let’s take a look at object destructuring in JavaScript

Destructuring is a concept that decomposes one of the data types and assigns its individual attributes to variables. It was introduced in the article "5 Common Scenarios and Examples of JavaScript Destructuring Assignment". Let’s review it today. one time.

Basic Destructuring

const fullName = {
    firstName: "Quintion",
    lastName: "Tang",
};
const { firstName, lastName } = fullName; // 解构语法
console.log(firstName); // Quintion
console.log(lastName); // Tang

As seen in the above code snippet, in the destructuring syntax, the firstName object property is decomposed and assigned to the expression left Variables defined on the side. In the above scenario, the object's property names should match the variables defined in the expression on the left. If you define other variable names, you will not get the desired value, such as:

const fullName = {
    firstName: "Quintion",
    lastName: "Tang",
};
const { firstName, trueName } = fullName; // 解构语法
console.log(firstName); // Quintion
console.log(trueName); // undefined

Since there is no attribute trueName in fullName, it is initialized to undefined.

Alias ​​destructuring

If you need to assign object attributes to variable names with inconsistent attribute names, you can implement it with the following code:

const fullName = {
    firstName: "Quintion",
    lastName: "Tang",
};
const { firstName: trueName, lastName } = fullName; // 解构语法
console.log(trueName); // Quintion
console.log(lastName); // Tang

Default value destructuring

As you can see in the above code, there is no destructuring of specific attributes in the object. Generally, the value is assigned to undefined. If you do not want it to be undefined, you can set a default value for it, as follows :

const fullName = {
    firstName: "Quintion",
    lastName: "Tang",
};
const { firstName: trueName, lastName, age = 18 } = fullName; // 解构语法
console.log(trueName); // Quintion
console.log(lastName); // Tang
console.log(age); // 18

Let’s take a look at the results under the age attribute:

const fullName = {
    firstName: "Quintion",
    lastName: "Tang",
    age: 30,
};
const { firstName: trueName, lastName, age = 18 } = fullName; // 解构语法
console.log(trueName); // Quintion
console.log(lastName); // Tang
console.log(age); // 30

REST deconstruction

If you want to deconstruct an attribute from an object, The remaining attribute structure is another variable, as follows:

const fullName = {
    firstName: "Quintion",
    lastName: "Tang",
    age: 30,
};
const { age, ...username } = fullName; // 解构语法
console.log(username); // { firstName: 'Quintion', lastName: 'Tang' }
console.log(age); // 30

In the above code snippet, the username attribute is assigned to a variable and uses rest## The # operator (...) assigns the remaining properties of the variable to a separate object.

Recommended learning: "

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