whatsapp-web.js/example.js

const fs = require('fs');
const { Client } = require('./index');

const SESSION_FILE_PATH = './session.json';
let sessionCfg;
if (fs.existsSync(SESSION_FILE_PATH)) {
    sessionCfg = require(SESSION_FILE_PATH);
}

const client = new Client({puppeteer: {headless: false}, session: sessionCfg});
// You can use an existing session and avoid scanning a QR code by adding a "session" object to the client options.
// This object must include WABrowserId, WASecretBundle, WAToken1 and WAToken2.

client.initialize();

client.on('qr', (qr) => {
    // NOTE: This event will not be fired if a session is specified.
    console.log('QR RECEIVED', qr);
});

client.on('authenticated', (session) => {
    console.log('AUTHENTICATED', session);

    if (!fs.existsSync(SESSION_FILE_PATH)) {
        fs.writeFile(SESSION_FILE_PATH, JSON.stringify(session), function(err) {
            if (err) {
                console.error(err);
            }
        });
    }
});

client.on('auth_failure', msg => {
    // Fired if session restore was unsuccessfull
    console.error('AUTHENTICATION FAILURE', msg);
});

client.on('ready', () => {
    console.log('READY');
});

client.on('message', async msg => {
    console.log('MESSAGE RECEIVED', msg);

    if (msg.body == '!ping reply') {
        // Send a new message as a reply to the current one
        msg.reply('pong');

    } else if (msg.body == '!ping') {
        // Send a new message to the same chat
        client.sendMessage(msg.from, 'pong');

    } else if (msg.body.startsWith('!subject ')) {
        // Change the group subject
        let chat = await msg.getChat();
        if(chat.isGroup) {
            let newSubject = msg.body.slice(9);
            chat.setSubject(newSubject);
        } else {
            msg.reply('This command can only be used in a group!');
        }
    } else if (msg.body.startsWith('!echo ')) {
        // Replies with the same message
        msg.reply(msg.body.slice(6));
    } else if (msg.body.startsWith('!desc ')) {
        // Change the group description
        let chat = await msg.getChat();
        if(chat.isGroup) {
            let newDescription = msg.body.slice(6);
            chat.setDescription(newDescription);
        } else {
            msg.reply('This command can only be used in a group!');
        }
    } else if (msg.body == '!leave') {
        // Leave the group
        let chat = await msg.getChat();
        if(chat.isGroup) {
            chat.leave();
        } else {
            msg.reply('This command can only be used in a group!');
        }
    } else if(msg.body.startsWith('!join ')) {
        const inviteCode = msg.body.split(' ')[1];
        try {
            await client.acceptInvite(inviteCode);
            msg.reply('Joined the group!');
        } catch(e) {
            msg.reply('That invite code seems to be invalid.');
        } 
    } else if(msg.body == '!groupinfo') {
        let chat = await msg.getChat();
        if(chat.isGroup) {
            msg.reply(`
                *Group Details*
                Name: ${chat.name}
                Description: ${chat.description}
                Created At: ${chat.createdAt.toString()}
                Created By: ${chat.owner.user}
                Participant count: ${chat.participants.length}
            `);
        } else {
            msg.reply('This command can only be used in a group!');
        }
    } else if(msg.body == '!chats') {
        const chats = await client.getChats();
        client.sendMessage(msg.from, `The bot has ${chats.length} chats open.`);
    } else if(msg.body == '!info') {
        let info = client.info;
        client.sendMessage(msg.from, `
            *Connection info*
            User name: ${info.pushname}
            My number: ${info.me.user}
            Platform: ${info.platform}
            WhatsApp version: ${info.phone.wa_version}
        `);
    } else if(msg.body == '!mediainfo' && msg.hasMedia) {
        const attachmentData = await msg.downloadMedia();
        msg.reply(`
            *Media info*
            MimeType: ${attachmentData.mimetype}
            Filename: ${attachmentData.filename}
            Data (length): ${attachmentData.data.length}
        `);
    } else if(msg.body == '!quoteinfo' && msg.hasQuotedMsg) {
        const quotedMsg = await msg.getQuotedMessage();

        quotedMsg.reply(`
            ID: ${quotedMsg.id._serialized}
            Type: ${quotedMsg.type}
            Author: ${quotedMsg.author || quotedMsg.from}
            Timestamp: ${quotedMsg.timestamp}
            Has Media? ${quotedMsg.hasMedia}
        `);
    } else if(msg.body == '!resendmedia' && msg.hasQuotedMsg) {
        const quotedMsg = await msg.getQuotedMessage();
        if(quotedMsg.hasMedia) {
            const attachmentData = await quotedMsg.downloadMedia();
            client.sendMessage(msg.from, attachmentData, {caption: 'Here\'s your requested media.'});
        }
        
    } else if(msg.body == '!location') {
        msg.reply(new Location(37.422, -122.084, 'Googleplex\nGoogle Headquarters'));
    } else if(msg.location) {
        msg.reply(msg.location);
    } else if(msg.body.startsWith('!status ')) {
        const newStatus = msg.body.split(' ')[1];
        await client.setStatus(newStatus);
        msg.reply(`Status was updated to *${newStatus}*`);
    } else if (msg.body == '!mention') {
        const contact = await msg.getContact();
        const chat = await msg.getChat();
        chat.sendMessage(`Hi @${contact.number}!`, {
            mentions: [contact]
        });
    }
});

client.on('message_create', (msg) => {
    // Fired on all message creations, including your own
    if(msg.fromMe) {
        // do stuff here
    }
});

client.on('message_revoke_everyone', async (after, before) => {
    // Fired whenever a message is deleted by anyone (including you)
    console.log(after); // message after it was deleted.
    if (before) {
        console.log(before); // message before it was deleted.
    }
});

client.on('message_revoke_me', async (msg) => {
    // Fired whenever a message is only deleted in your own view.
    console.log(msg.body); // message before it was deleted.
});

client.on('disconnected', (reason) => {
    console.log('Client was logged out', reason);
});