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我是Node.js和Google Gmail API的noob。但是，我熟悉客户端JavaScript。我能够分析代码并理解它。Node.js Gmail API如何访问电子邮件的内容？
我能够按照本指南（https://developers.google.com/gmail/api/quickstart/nodejs）访问标签，在我的Gmail帐户（下面的代码）：
var fs = require('fs');
var readline = require('readline');
var google = require('googleapis');
var googleAuth = require('google-auth-library');
// If modifying these scopes, delete your previously saved credentials
// at ~/.credentials/gmail-nodejs-quickstart.json
var SCOPES = ['https://www.googleapis.com/auth/gmail.readonly'];
var TOKEN_DIR = (process.env.HOME || process.env.HOMEPATH ||
process.env.USERPROFILE) + '/.credentials/';
var TOKEN_PATH = TOKEN_DIR + 'gmail-nodejs-quickstart.json';
// Load client secrets from a local file.
fs.readFile('client_secret.json', function processClientSecrets(err, content) {
if (err) {
console.log('Error loading client secret file: ' + err);
return;
}
// Authorize a client with the loaded 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) {
var clientSecret = credentials.installed.client_secret;
var clientId = credentials.installed.client_id;
var redirectUrl = credentials.installed.redirect_uris[0];
var auth = new googleAuth();
var oauth2Client = new auth.OAuth2(clientId, clientSecret, redirectUrl);
// Check if we have previously stored a token.
fs.readFile(TOKEN_PATH, function(err, token) {
if (err) {
getNewToken(oauth2Client, callback);
} else {
oauth2Client.credentials = 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 to call with the authorized
* client.
*/
function getNewToken(oauth2Client, callback) {
var authUrl = oauth2Client.generateAuthUrl({
access_type: 'offline',
scope: SCOPES
});
console.log('Authorize this app by visiting this url: ', authUrl);
var rl = readline.createInterface({
input: process.stdin,
output: process.stdout
});
rl.question('Enter the code from that page here: ', function(code) {
rl.close();
oauth2Client.getToken(code, function(err, token) {
if (err) {
console.log('Error while trying to retrieve access token', err);
return;
}
oauth2Client.credentials = token;
storeToken(token);
callback(oauth2Client);
});
});
}
/**
* Store token to disk be used in later program executions.
*
* @param {Object} token The token to store to disk.
*/
function storeToken(token) {
try {
fs.mkdirSync(TOKEN_DIR);
} catch (err) {
if (err.code != 'EEXIST') {
throw err;
}
}
fs.writeFile(TOKEN_PATH, JSON.stringify(token));
console.log('Token stored to ' + TOKEN_PATH);
}
/**
* Lists the labels in the user's account.
*
* @param {google.auth.OAuth2} auth An authorized OAuth2 client.
*/
function listLabels(auth) {
var gmail = google.gmail('v1');
gmail.users.labels.list({
auth: auth,
userId: 'me',
}, function(err, response) {
if (err) {
console.log('The API returned an error: ' + err);
return;
}
var labels = response.labels;
if (labels.length == 0) {
console.log('No labels found.');
} else {
console.log('Labels:');
for (var i = 0; i < labels.length; i++) {
var label = labels[i];
console.log('- %s', label.name);
}
}
});
}
根据（https://developers.google.com/gmail/api/v1/reference/users/messages/delete#javascript），该代码将允许我阅读电子邮件。但是，虽然页面（上面链接）解释了以下功能的参数，但它并不解释如何获取消息ID。该函数要求一个整数（我猜）来确定要返回哪条消息。但是，没有信息解释如何首先获得message ID。我是否应该使用循环并获取所有电子邮件，然后找出我想要的？ message ID应该是什么？代码如下：
/**
* Delete Message with given ID.
*
* @param {String} userId User's email address. The special value 'me'
* can be used to indicate the authenticated user.
* @param {String} messageId ID of Message to delete.
*/
function deleteMessage(userId, messageId) {
var request = gapi.client.gmail.users.messages.delete({
'userId': userId,
'id': messageId
});
request.execute(
function(resp) { });
}
谢谢。