ReactJS componentDidMount，獲取Spotify API和Promise

Question

我正在學習如何使用ReactJS，Spotify API和Promise。 我正在嘗試在Spotify上獲取音樂家熱門專輯並播放30秒的曲目。

我正在使用一個名為spotify-web-api-node的Spotify軟件包，我想我不了解React或JS的基本內容。 Syntax error: Unexpected token, expected ( (11:8)

從'react'導入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

你使用spotify-api提供的承諾的方式是正確的。 但是，您不應該從componentDidMount返回Promise 。 React沒有任何用處。

而只是在componentDidMount運行基於promise的函數。

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);
    });
}

您也可以在導入后立即將Q設置為承諾提供商。

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

Answer 2

你不能在類這樣的類中有一個const定義。

您應該將其移到外面或刪除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 {

要么

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
  });