【es11】es11的新特性整理(13)
这里整理了ES11新增的特性。
<!DOCType html>
<html>
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
<script>
console.log("-------------- 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;
}
printPerson() {
console.log(girl.name);
console.log(girl.#age);
console.log(girl.#weight);
}
}
const girl = new Person('小红', 18, '50kg');
console.log(girl.name);
//console.log(girl.#age); // SyntaxError: Private field '#age' must be declared in an enclosing class
girl.printPerson(); // 小红 18 50kg
}
console.log("-------------- Promise.allSettled --------------");
{
const p1 = new Promise((resolve, reject) => {
setTimeout(() => {
resolve('商品数量 - 1');
}, 1000);
});
const p2 = new Promise((resolve, reject) => {
setTimeout(() => {
resolve('商品数量 - 2');
}, 1000);
});
const p3 = new Promise((resolve, reject) => {
setTimeout(() => {
reject('没有商品');
}, 1000);
});
//调用 allsettled 方法，返回一个Promise对象，该对象的状态取决于所有Promise对象的状态。
const result = Promise.allSettled([p1, p2, p3]);
console.log(result);
/*
Promise {<pending>}
[[Prototype]]: Promise
[[PromiseState]]: "fulfilled"
[[PromiseResult]]: Array(3)
0: {status: 'fulfilled', value: '商品数量 - 1'}
1: {status: 'fulfilled', value: '商品数量 - 2'}
2: {status: 'rejected', reason: '没有商品'}
length: 3
[[Prototype]]: Array(0)
*/
//Promise.all 只有全部成功了才返回成功， allsettled则不是
const result1 = Promise.all([p1, p2]);
console.log(result1);
/*
Promise {<pending>}
[[Prototype]]: Promise
[[PromiseState]]: "fulfilled"
[[PromiseResult]]: Array(2)
0: "商品数量 - 1"
1: "商品数量 - 2"
length: 2
[[Prototype]]: Array(0)
*/
const result2 = Promise.all([p1, p2, p3]);
console.log(result2);
/*
Promise {<pending>}[[Prototype]]: Promise
[[PromiseState]]: "rejected"
[[PromiseResult]]: "没有商品"
Uncaught (in promise) 没有商品
*/
}
console.log("-------------- 可选链操作符 --------------");
{
function main(config) {
const dbHost = config && config.db && config.db.host;
console.log(dbHost)
}
main({
db: {
host: '127.0.0.1',
username: 'root'
},
cache: {
host: '192.168.1.1',
username: 'admin'
}
}); //127.0.0.1
function main1(config) {
const dbHost = config.db.host;
console.log(dbHost)
}
// main1(); // TypeError: Cannot read properties of undefined
function main2(config) {
const dbHost = config?.db?.host;
console.log(dbHost)
}
main2(); //undefined
main2({
db: {
host: '127.0.0.1',
username: 'root'
},
cache: {
host: '192.168.1.1',
username: 'admin'
}
}); //127.0.0.1
}
console.log("-------------- BigInt --------------");
{
let n = 123;
console.log(BigInt(n)); //123n
//console.log(BigInt(12.2)); //The number 12.2 cannot be converted to a BigInt because it is not an integer
console.log(Number.MAX_SAFE_INTEGER); //9007199254740991
//BigInt 运算需要和BigInt进行运算
console.log(BigInt(Number.MAX_SAFE_INTEGER) + BigInt(10)); //9007199254741001n
}
console.log("-------------- globalThis --------------");
{
console.log(globalThis); //Window {...}
console.log(globalThis === window); //true
console.log(globalThis === global); //true
}
</script>
</body>
</html>
欢迎大家的意见和交流
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