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ECMASript 11新特性

2022-03-18 21:05:18 作者：互联网

ES11语法新特性

私有属性

class Person {
    //公有属性
    name;
    //私有属性
    #age;
    #weight;//构造方法
    constructor(name, age, weight) {
        this.name = name;
        this.#age = age;
        this.#weight = weight;
    }

    intro() {
        console.log(girl.name);
        console.log(girl.#age);
        console.log(girl.#weight);
    }
}
//实例化
const girl = new Person('小红', 18, '45kg');
// console.log(girl.name);
// console.log(girl.#age);
// console.log(girl.#weight);
//无法在类的外部直接调用
//Uncaught SyntaxError: Private field '#age' must be declared in an enclosing class

girl.intro();//可以通过内部方法进行调用

Promise.allSettled

//声明两个promise对象
const p1 = new Promise((resolve, reject) => {
    setTimeout(() => {
        resolve('商品数据-1');
    }, 1000)
});
const p2 = new Promise((resolve, reject) => {
    setTimeout(() => {
        //resolve('商品数据-2');
        reject('出错啦!');
    }, 1000)
});

//调用  allsettled 方法
//可以检测所有对象的promise的成功和失败
// const result = Promise.allSettled([p1,p2]);

//全部成功才会返回成功的promise
const res = Promise.all([p1,p2])

console.log(res);

String.prototype.matchAll

let str =
    `<ul>
        <li>
            <a>肖生克的救赎</a>
            <p>上映日期:1994-09-10</p></li>
        <li>
            <a>阿甘正传</a>
            <p>上映日期:1994-07-06</p></li>

    </ul>`;

const reg = /<li>.*?<a>(.*?)<\/a>.*?<p>(.*?)<\/p>/sg;

//调用方法
//用来得到正则批量匹配的结果
const result = str.matchAll(reg);

// for( let v of result){
// console.log(v);
// }

const arr = [...result];
console.log(arr);

可选链操作符

    // const dbHost = config && config.db && config.db.host;
    //当检测前面参数传入以后再往后进行
    const dbHost = config?.db?.host;
    console. log(dbHost);
}
main({
    db: {
        host: ' 192.168.1.100', 
        username: 'root',
    },
    cache: {
        host: '192.168.1.200', 
        username: 'admin',
    }
})

动态import

在需要的时候再引入，可以减少运算

<body>
    <script src="./app.js" type="module"></script>
    <button id="btn">按钮</button>
</body>

// import * as mq from "./hello"
//获取元素
const btn = document.getElementById( 'btn' );

btn.onclick = function(){
    import( './hello' ).then(module => {
        module.hello();
        });
}

function hello() {
    alert(hello);
}

数据类型BigInt

//大整形
let n = 521n;
console.log(n, typeof (n));

let n2 = 123;
console.log(BigInt(n2));
//console.log(BigInt(3.1415926));//不支持浮点运算

//大数值运算
let max = Number.MAX_SAFE_INTEGER;
console.log(max);
console.log(max + 1);
console.log(max + 2);
console.log(BigInt(max))
console.log(BigInt(max) + BigInt(1));
console.log(BigInt(max) + BigInt(2))

特殊变量globalThis

支持JS和Node,js

无论执行环境是什么，始终都指向全局对象

标签：11,const,log,max,特性,BigInt,console,girl,ECMASript
来源： https://www.cnblogs.com/wzx-blog/p/16023551.html