How to a send message in a channel when the bot is ready?

Question

I was trying to modify the "ping pong" sample code in discord.js.
Instead of logging in the console, I wanted to send a message in a specific channel in Discord. I have tried using the code below to do it but it keeps showing me this error:

(node:10192) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'channels' of undefined
    at Client.<anonymous> (D:\GAMES\DiscordBot\index.js:7:12)

This is the code I'm using:

const Discord = require('discord.js');
const client = new Discord.Client();

console.log(client);

client.on('ready', client => {
  client.channels.get('787667808777998851').send('Hello here!');
});

client.on('message', msg => {
  if (msg.content === 'ping') {
    msg.reply('pong');
  }
});

client.login('auth-token');

Answer 1

Simple mistake! You are declaring an new client variable which is undefined since the ready event doesn't callback with any values. Also .get isn't a function. What you're looking for is .fetch and this function returns a promise that resolves to a channel. Here is your new ready event.

client.on('ready', () => {
    client.channels.fetch('787667808777998851')
    .then(channel => {
        channel.send("Hello here!");
    })
});

Also, try not to post your bot token in your question. It's very dangerous and gives anyone access to your bot.