ES6 特性

let 和 const

箭头函数

模板字符串

解构赋值

const obj = { a: 1, b: 2 };
const { a, b } = obj;
console.log(a, b); // 1, 2

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

默认参数

function foo(a, b = 2, c = 3) {}

剩余（rest）参数

function sum(...nums) {
  return nums.reduce((a, b) => a + b);
}
sum(1, 2, 3, 4, 5);

扩展运算符

const arr1 = [1, 2, 3];
const arr2 = [...arr, 4, 5];

const obj1 = { a: 1, b: 2 };
const obj2 = { ...obj, c: 3 };

扩展对象字面量

对象属性简写

const name = "zhangsan";
const age = 18;
const preson = { name, age };

对象方法简写

const person = {
  name: "zhangsan",
  greet() {
    console.log("Hello！");
  },
};

for…of 循环

模块化（import/export）

// foo.js
export const foo = () => {};

// main.js
import { foo } from "./foo";

默认导出

// foo.js
export default () => {};

// main.js
import foo from "./foo";
foo();

类（class）

class Person {
  constructor(name) {
    this.name = name;
  }
  say() {}
}

class Student extends Person {
  say() {
    console.log(`I'm a student, ${this.name}`);
  }
}
const s = new Student("zhangsan");
s.say();

Promise

Symbol

生成器和迭代器

Set 和 Map

静态方法

class MathUtil {
  static add(a, b) {
    return a + b;
  }
}
console.log(MathUtil.add(1, 2));

字符串新方法

• startsWith
• endsWith
• includes

数组新方法

• find
• findIndex

对象合并

const obj1 = { a: 1, b: 2 };
const obj2 = { b: 3, c: 5 };
const obj3 = { ...obj1, ...obj2 };

空值合并运算符

const foo = null ?? "default";
const bar = 0 ?? 42;
console.log(bar); // 0

块级作用域

Proxy

Proxy 对象用于创建一个对象的代理，从而实现基本操作的拦截和自定义（如属性查找、赋值、枚举、函数调用等）。

const target = {
  message: "hello world",
};
const handler = {
  get: (obj, prop) => {
    return prop in obj ? obj[prop] : "not fount prop";
  },
  set: (obj, prop, value) => {
    return value;
  },
};
const proxy = new Proxy(target, handler);