处理多个Promise: .all() .race()

约定不等于承诺〃 2021-12-01 11:48 330阅读 0赞

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <meta http-equiv="X-UA-Compatible" content="ie=edge">
        <title>处理多个Promise</title>
    </head>
    <body>
        <script>
             /*
            Promise.all() 方法回傳一個 Promise 物件，當引數 iterable 中所有的 promises 都被實現（resolved）。
            或以第一個被拒絕的 promise 的原因被拒絕。
            */
            //reslove
            const usersPromise=new Promise((reslove,reject)=>{
                setTimeout(()=>{
                    reslove(['Simba','PumbaaPig','NANA'])
                },2000);
            })
    
            const moviePromise=new Promise((reslove,reject)=>{
                setTimeout(()=>{
                    reslove({name:'狮子王',rating:8.9,year:2019})
                },600)
            });
    
            Promise
            .all([usersPromise,moviePromise])
            .then(responses=>{
                const [users,movide]=responses;
                console.log(users);//(3) ["Simba", "PumbaaPig", "NANA"]
                console.log(movide);//{name: "狮子王", rating: 8.9, year: 2019}
            })
    
    
            //reject
            const usersPromise1=new Promise((reslove,reject)=>{
                setTimeout(()=>{
                    reslove(['Simba','PumbaaPig','NANA'])
                },2000);
            })
    
            const moviePromise1=new Promise((reslove,reject)=>{
                setTimeout(()=>{
                    reject(Error('NO movie'));
                },600)
               
            });
            Promise
            .all([usersPromise1,moviePromise1])
            .then(responses=>{
                const [users1,movide1]=responses;
                console.log(users1);//(3) ["Simba", "PumbaaPig", "NANA"]
                console.log(movide1);//NO movie
            })
    
    
    
    
    
    
            /*
            Promise.race(iterable) 方法返回一个 promise,一旦迭代器中的某个promise解决或拒绝，
            返回的 promise就会解决或拒绝。
            */
    
            //谁快就打印谁
            const usersPromise2=new Promise((reslove,reject)=>{
                setTimeout(()=>{
                    reslove(['Simba','PumbaaPig','NANA'])
                },2000);
            })
    
            const moviePromise2=new Promise((reslove,reject)=>{
                setTimeout(()=>{
                    reslove({name:'狮子王',rating:8.9,year:2019})
                },600)
            })
    
            Promise
            .race([usersPromise2,moviePromise2])
            .then(responses=>{
                console.log(responses);//{name: "狮子王", rating: 8.9, year: 2019}
            })
            .catch(err=>{
                console.error(err);
            })
    
    
            //有错误也是一样的，还是不能影响谁快就打印谁的定律
            const usersPromise3=new Promise((reslove,reject)=>{
                setTimeout(()=>{
                    reject(Error('拒绝、错误'))
                },2000);
            })
    
            const moviePromise3=new Promise((reslove,reject)=>{
                setTimeout(()=>{
                    reslove({name:'狮子王',rating:8.9,year:2019})
                },600)
            })
    
            Promise
            .race([usersPromise3,moviePromise3])
            .then(responses=>{
                console.log(responses);//{name: "狮子王", rating: 8.9, year: 2019}
            })
            .catch(err=>{
                console.error(err);
            })
    
    
    
    
    
    
        </script>
    </body>
    </html>