ES6+ 特性 #

// 数组解构
const [a, b, c] = [1, 2, 3];

// 对象解构
const { name, age } = { name: '张三', age: 25 };

// 默认值
const { x = 0, y = 0 } = {};

// 数组展开
const arr1 = [1, 2, 3];
const arr2 = [...arr1, 4, 5]; // [1, 2, 3, 4, 5]

// 对象展开
const obj1 = { a: 1, b: 2 };
const obj2 = { ...obj1, c: 3 }; // { a: 1, b: 2, c: 3 }

// Promise
fetch('https://api.example.com/data')
    .then(response => response.json())
    .then(data => console.log(data))
    .catch(error => console.error(error));

// async/await
async function fetchData() {
    try {
        const response = await fetch('https://api.example.com/data');
        const data = await response.json();
        console.log(data);
    } catch (error) {
        console.error(error);
    }
}

// 导出
export const PI = 3.14159;
export function add(a, b) {
    return a + b;
}
export default class Calculator {
    // ...
}

// 导入
import Calculator, { PI, add } from './math.js';

class Person {
    constructor(name, age) {
        this.name = name;
        this.age = age;
    }
    
    greet() {
        console.log(`你好，我是${this.name}`);
    }
}

class Student extends Person {
    constructor(name, age, grade) {
        super(name, age);
        this.grade = grade;
    }
    
    study() {
        console.log(`${this.name}正在学习`);
    }
}

// 可选链
const userName = user?.profile?.name;

// 空值合并
const displayName = userName ?? '访客';