ReactJS componentDidMount，获取Spotify API和Promise

Question

I'm learning how used ReactJS, Spotify API, and Promise. I'm trying to fetch musician top albums on Spotify and play 30 seconds of the track.

I'm using a Spotify package called spotify-web-api-node I think I'm not understanding something fundamental about React or JS. Syntax error: Unexpected token, expected ( (11:8)

import React from 'react';

import SpotifyWebApi from 'spotify-web-api-node';
require('dotenv').config();


export default class SpotifyComponent extends React.Component {
  // Create the api object with the credentials
  const spotifyApi = new SpotifyWebApi({
    clientId : process.env.REACT_APP_SPOTIFY_CLIENT_ID,
    clientSecret : process.env.REACT_APP_SPOTIFY_CLIENT_SECRET
  });
// Save the access token so that it's used in future calls
  componentDidMount() {
    **(11:8)** --> return spotifyApi = new Promise((resolve, reject) => {
      spotifyApi.clientCredentialsGrant()

      .then( => (data) {
        console.log('The access token expires in ' + data.body['expires_in']);
        console.log('The access token is ' + data.body['access_token']);
      });

      // using Promises through Promise, Q or when - get Elvis' albums in range [20...29]
      spotifyApi.getArtistAlbums('43ZHCT0cAZBISjO8DG9PnE', {limit: 10, offset: 20})
        .then(function(data) {
          console.log('Album information', data);
        }, function(err) {
          console.error(err);
        });
    });

    SpotifyWebApi.setPromiseImplementation(Q);
  }
}

Answer 1

The way you're using the promises provided by the spotify-api are correct. However you shouldn't return a Promise from componentDidMount . React doesn't have any use for it.

Instead just run your promise based functions inside componentDidMount .

componentDidMount() {

  // the next line will actually trigger the promise to run
  spotifyApi.clientCredentialsGrant()
    .then((data) => { // this line was missing "=>" in your original code
      console.log('The access token expires in ' + data.body['expires_in']);
      console.log('The access token is ' + data.body['access_token']);
    });

  // the next line also triggers a promise to run
  spotifyApi.getArtistAlbums('43ZHCT0cAZBISjO8DG9PnE', {limit: 10, offset: 20})
    .then(function(data) {
      console.log('Album information', data);
    }, function(err) {
      console.error(err);
    });
}

Also you can set Q as the promise provider right after your import.

import SpotifyWebApi from 'spotify-web-api-node';
SpotifyWebApi.setPromiseImplementation(Q);

Answer 2

You can't have a const definition inside of a class like that.

You should either move it outside or remove the const :

// Create the api object with the credentials
const spotifyApi = new SpotifyWebApi({
  clientId : process.env.REACT_APP_SPOTIFY_CLIENT_ID,
  clientSecret : process.env.REACT_APP_SPOTIFY_CLIENT_SECRET
});

export default class SpotifyComponent extends React.Component {

or

export default class SpotifyComponent extends React.Component {
  // Create the api object with the credentials
  spotifyApi = new SpotifyWebApi({
    clientId : process.env.REACT_APP_SPOTIFY_CLIENT_ID,
    clientSecret : process.env.REACT_APP_SPOTIFY_CLIENT_SECRET
  });