Object Spread Operator

实例1

const animals = {
    tiger: 23,
    lion:5,
    monkey: 2
}

const {tiger, ...rest} = animals;

console.log(tiger) //输出:23
console.log(rest)  //输出: {lion:5, monkey: 5}

实例2

const array = [1,2,3,4,5]
function sum(a,b,c,d,e){
    return a+b+c+d+e
}
//...array,所有参数
sum(...array)  //输出: 15

实例3

const animals = {
    tiger: 23,
    lion:5,
    monkey: 2,
    bird: 40
}

const {tiger, lion,...rest} = animals;

function objectSpread(p1,p2,p3){
    console.log(p1);
    console.log(p2);
    console.log(p3);
}
//同样可试用于对象
objectSpread(tiger,lion,rest)
/*输出:
23
5
{monkey: 2, bird: 40}*/

finally

const urls = [
    'https://jsonplaceholder.typicode.com/users',
    'https://jsonplaceholder.typicode.com/posts',
    'https://jsonplaceholder.typicode.com/albums'
]

Promise.all(urls.map(url=>
    fetch(url).then(resp=>resp.json())
)).then(arrays=>{
    //throw Error  
    console.log('users',arrays[0])
    console.log('posts',arrays[1])
    console.log('albums',arrays[2])
}).catch(err=>console.log('fix it',err))
    .finally(() => console.log('extra'))
    
/*不论catch是否捕获异常，finally永远会执行*/

for await of

const urls = [
    'https://jsonplaceholder.typicode.com/users',
    'https://jsonplaceholder.typicode.com/posts',
    'https://jsonplaceholder.typicode.com/albums'
]

const getData = async function(){
    try {
        const [users,posts,albums] = await Promise.all(urls.map(url=>
        fetch(url).then(resp=>resp.json())
        ))
        console.log('users',users)
        console.log('posts',posts)
        console.log('albums',albums)
    } catch (error) {
        console.log(error)
    }
}
//for await of
const getData2 = async function(){
    const arraysOfPromises=urls.map(url=>fetch(url));
    for await (let request of arraysOfPromises){
        const data = await request.json();
        console.log(data)
    }
}
getData2()