index.js

const fs = require('fs');
const readline = require('readline');
const {google} = require('googleapis');
let mailparser = require('mailparser')
var htmlBody='';
var dict1 = "10";

// If modifying these scopes, delete token.json.
const SCOPES = ['https://www.googleapis.com/auth/gmail.readonly'];
// The file token.json stores the user's access and refresh tokens, and is
// created automatically when the authorization flow completes for the first
// time.
const TOKEN_PATH = 'token.json';

const SSU_Helper = require('../../Objects/SSU_Common/SSU_Helper');
const { catchEmailBody } = require('../../Objects/SSU_Common/SSU_Helper');

// Load client secrets from a local file.
fs.readFile('credentials.json', (err, content) => {
  if (err) return console.log('Error loading client secret file:', err);
  // Authorize a client with credentials, then call the Gmail API.
  authorize(JSON.parse(content), listLabels);
});

/**
 * Create an OAuth2 client with the given credentials, and then execute the
 * given callback function.
 * @param {Object} credentials The authorization client credentials.
 * @param {function} callback The callback to call with the authorized client.
 */
 function authorize(credentials, callback) {
  console.log("----------------A----------------------");
  const {client_secret, client_id, redirect_uris} = credentials.installed;
  const oAuth2Client = new google.auth.OAuth2(
      client_id, client_secret, redirect_uris[0]);

  // Check if we have previously stored a token.
  fs.readFile(TOKEN_PATH, (err, token) => {
    if (err) return getNewToken(oAuth2Client, callback);
    oAuth2Client.setCredentials(JSON.parse(token));
    callback(oAuth2Client);
  });
}

/**
 * Get and store new token after prompting for user authorization, and then
 * execute the given callback with the authorized OAuth2 client.
 * @param {google.auth.OAuth2} oAuth2Client The OAuth2 client to get token for.
 * @param {getEventsCallback} callback The callback for the authorized client.
 */
 function getNewToken(oAuth2Client, callback) {
  console.log("----------------B----------------------");
  const authUrl = oAuth2Client.generateAuthUrl({
    access_type: 'offline',
    scope: SCOPES,
  });
  console.log('Authorize this app by visiting this url:', authUrl);
  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
  });
  rl.question('Enter the code from that page here: ', (code) => {
    rl.close();
    oAuth2Client.getToken(code, (err, token) => {
      if (err) return console.error('Error retrieving access token', err);
      oAuth2Client.setCredentials(token);
      // Store the token to disk for later program executions
      fs.writeFile(TOKEN_PATH, JSON.stringify(token), (err) => {
        if (err) return console.error(err);
        console.log('Token stored to', TOKEN_PATH);
      });
      callback(oAuth2Client);
    });
  });
}

function listMessages(auth, query){
  console.log("----------------D----------------------");
    query = 'salesforce.sales@deliveryhero.com';
    return new Promise((resolve, reject) => {    
      const gmail = google.gmail({version: 'v1', auth});
      gmail.users.messages.list(      
        {        
          userId: 'me',  
          q:query,      
          maxResults:5     
        },            (err, res) => {        
          if (err) {                    reject(err);          
            return;        
          }        
          if (!res.data.messages) {                    resolve([]);          
            return;        
          }                resolve(res.data);  

                           getMail(res.data.messages[0].id, auth);
        }    
      );  
    })
  }

  fs.readFile('credentials.json', (err, content) => {
    console.log("----------------E----------------------");
    if (err) return console.log('Error loading client secret file:', err);
    // Authorize a client with credentials, then call the Gmail API.
    authorize(JSON.parse(content), listMessages);

  });

  function getMail(msgId, auth){

    console.log("----------------F----------------------");
    console.log(msgId)
    const gmail = google.gmail({version: 'v1', auth});
    //This api call will fetch the mailbody.
    gmail.users.messages.get({
        userId:'me',
        id: msgId ,
    }, (err, res) => {
      console.log(res.data.labelIds.INBOX)
        if(!err){
          console.log("no error")
            var body = res.data.payload.parts[0].body.data;

            htmlBody = Buffer.from((body.replace(/-/g, '+').replace(/_/g, '/')), "base64").toString();

console.log（htmlbody）

}
    });
  }

gmail.js

class Gmail {
 gmailIntegration(){
        const output = execSync('cd ./Objects/email_common; node index.js', { encoding: 'utf-8' });  // the default is 'buffer'
        console.log('Output was:\n', output);

}

我有两个文件index.js和gmail.js，在gmail类的gmailintegration（）方法中，我使用exexsync命令通过终端运行index.js，它会将htmlbody打印到控制台，但我需要使用gmail类中gmailintegration（）函数中的htmlbody变量，如何从gmailintegration（）函数中的index.js访问htmlbody变量？