ES6 in to resolve Promise

In JavaScript, all code is single-threaded execution.

1. Test whether the browser supports Promise

        'use strict';

        new Promise(function(){});

        console.log ( 'Support Promise!');

2.

    <-! Axios is based on the promise of a HTTP library, you can use the browser
    和node.js中 -->
    <script src="https://cdnjs.cloudflare.com/ajax/libs/axios/0.19.0/axios.min.js">
    </script>
    <script>
        let username;
        const usersPromise=axios.get('https://api.github.com/users')
        // 监听事件
        usersPromise.then(reponse=>{
            // console.log(reponse);
            username=reponse.data[0].login;
            // 返回promise
            return axios.get(`https://api.github.com/users/${username}/repos`);
        }).then(reponse=>{
            console.log(reponse.data);
        })
        // listens error occurs the catch 
        . The catch (ERR => {
            console.error(err)
        })
    </script>

reponse data inside

3. Practice Code

(1) promise success stories reslove (to change the parameter name)

        // reslove incoming data successful 
        // if it fails to return to reject information 
        const = the p- new new Promise ((reslove, reject) => {
            setTimeout(()=>{
                reslove('This is successful')
            },2000);
        })
        p.then (Data => {
             // successful information 
            console.log (data);
        })

 (2) promise failures reject (to change the parameter name)

        // reslove incoming data successful 
        // if it fails to return to reject information 
        const = the p- new new Promise ((reslove, reject) => {
            setTimeout(()=>{
                reject('This is successful')
            },2000);
        })
        p.then(data=>{
            console.log(data);
        .}) The catch (ERR => {
            // failure information 
            console.error (err);
        })

 4. promise of using a plurality of

　　Promise.all (iterable) method returns an instance Promise

　  All are within iterable parameter promise success callback is completed, if there is a failed promise parameters so the callback instance failure. Failure to find catch inside the code     

Promise.race (iterable) method returns a promise, once the iterator a promise to solve or refuse to return to the promise will be resolved or rejected. Note that the timer time: tip.

 

        const usersPromise=new Promise((resolve,reject)=>{

            setTimeout(()=>{

                resolve(['mojombo','vanpelt','wycats']);

            },2000);

        });

        const moviePromise=new Promise((resolve,reject)=>{

            setTimeout(()=>{

                // resolve ({name: 'wrestling it Dad!', Rating: 9.2, year: 2019});

                reject(Error('No moviePromise'))

            },500);

        });

        // Promise.all([usersPromise,moviePromise])

        Promise.race([usersPromise,moviePromise])

        .then(responses=>{

            // deconstruction assignment

            const [users,movie]=responses;

            console.log(users);

            console.log(movie);

        })

        .catch(err=>{

            console.error(err);

        })