4 分钟再快速过一遍 ES12 的 5 个要点~

// 十进制数字，按照千位进行划分
let n1 = 1_000_000_000;
console.log(n1); // This will print: 1000000000
// 十进制数字，按照千位进行划分，带小数点
let n2 = 1_000_000_000.150_200
console.log(n2); // This will print: 1000000000.1502
// 十六进制数字，按照字节分组
let n3 = 0x95_65_98_FA_A9
console.log(n3); // This will print: 641654651561
// 大文字，按千位划分
let n4 = 155_326_458_156_248_168_514n
console.log(n4); // This will print: 155326458156248168514n

// 声明一个字符串
const orgStr = 'JavaScript, often abbreviated as JS, is a programming language that conforms to the ECMAScript specification. JavaScript is high-level, often just-in-time compiled and multi-paradigm.';
// 用 replace 替换第一个选中元素
let newStr = orgStr.replace('JavaScript', 'TypeScript');
console.log(newStr);
// 用 replaceAll 替换所有选中元素
let newStr2 = orgStr.replaceAll('JavaScript', 'TypeScript');
console.log(newStr2);

// 创建 promise1
const promise1 = new Promise((resolve, reject) => {
    // 2 秒后 resolve
    setTimeout(() => resolve("The first promise has been resolved."), 2000);
});
// 创建 promise2
const promise2 = new Promise((resolve, reject) => {
    // 1 秒后 resolve
    setTimeout(() => resolve("The second promise has been resolved."), 1000);
});
// 创建 promise3
const promise3 = new Promise((resolve, reject) => {
    // 3 秒后 resolve
    setTimeout(() => resolve("The third promise has been resolved."), 3000);
});
(async function () {
    const data = await Promise.any([promise1, promise2, promise3]);
    // 第一个 resolve 后，立即返回给 data
    console.log(data);
    // 打印信息: The second promise has been resolved.
})();

// 创建 promise1
const promise1 = new Promise((resolve, reject) => {
    // After 1 second reject the first promise.
    setTimeout(() => reject("The first promise has been rejected."), 1000);
});
// 创建 promise2
const promise2 = new Promise((resolve, reject) => {
    // After 500 miliseconds reject the second promise.
    setTimeout(() => reject("The second promise has been rejected."), 500);
});
// 立即执行
(async function () {
    try {
        const data = await Promise.any([promise1, promise2]);
        console.log(data);
    } catch (error) {
        // 全部 Promise reject 则返回；
        console.log("Error: ", error);
        // 打印信息：Error:  AggregateError: All promises were rejected
    }
})();

// 当 ||= 左侧的值是 false，则更改赋值为等号后的值
let myPlaylist = {songsCount: 0, songs:[]};
myPlaylist.songsCount ||= 100;
console.log(myPlaylist); // This will print: {songsCount: 100, songs: Array(0)}
复制代码

// 当 &&= 左侧的值是 true，则更改赋值为等号后的值
let myFiles = {filesCount: 100, files:[]};
myFiles.filesCount &&= 5;
console.log(myFiles); // This will print: {filesCount: 5, files: Array(0)}

// 当 ??= 左侧的值是 null or undefined，则更改赋值为等号后的值
let userDetails = {firstname: 'Katina', age: 24}
userDetails.lastname ??= 'Dawson';
console.log(userDetails); // This will print: {firstname: 'Katina', age: 24, lastname: 'Dawson'}

// 创建 User 类
class User {
    constructor() {}
    // 加 # 井号设为私有方法
    #generateAPIKey() {
        return "d8cf946093107898cb64963ab34be6b7e22662179a8ea48ca5603f8216748767";
    }
    getAPIKey() {
        // 调用私有方法
        return this.#generateAPIKey();
    }
}
const user = new User();
const userAPIKey = user.getAPIKey();
console.log(userAPIKey); // This will print: d8cf946093107898cb64963ab34be6b7e22662179a8ea48ca5603f8216748767

// 创建 Str 类
class Str {
    // 设置私有属性
    #uniqueStr;
    constructor() {}
    // 私有 Setter
    set #generateUniqueStringByCustomLength(length = 24) {
        const characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
        let randomStr = "";
        for (let i = 0; i < length; i++) {
            const randomNum = Math.floor(Math.random() * characters.length);
            randomStr += characters[randomNum];
        }
        this.#uniqueStr = randomStr;
    }
    // 公共 Setter
    set setRandomString(length) {
        this.#generateUniqueStringByCustomLength = length;
    }
    // 私有 Getter
    get #fetchUniqueString() {
        return this.#uniqueStr;
    }
    // 公共 Getter
    get getRandomString() {
        return this.#fetchUniqueString;
    }
}
const str = new Str();
// 调用公共 Setter，然后访问私有 Setter
str.setRandomString = 20;
// 调用公共 Getter，然后访问私有 Getter
const uniqueStr = str.getRandomString;
console.log(uniqueStr); // 每次在 Setter 之后执行 Getter ，将打印一个随机字符串