// Set the bot's "Playing: " status (must be in an event!)
client.on("ready", () => {
    client.user.setActivity("my code", { type: "WATCHING"})
})

// Set the bot's online/idle/dnd/invisible status
client.on("ready", () => {
    client.user.setStatus("online");
});

// Set the bot's presence (activity and status)
client.on("ready", () => {
    client.user.setPresence({
        game: { 
            name: 'my code',
            type: 'WATCHING'
        },
        status: 'idle'
    })
})

client.on("ready", () => {
    client.user.setActivity("my code", { type: "STREAMING", url: "https://www.twitch.tv/something" })
})

// Get a User by ID
client.users.get("user id here");
// Returns <User>

// Get a Member by ID
message.guild.members.get("user ID here");
// Returns <Member>

// Get a Member from message Mention
message.mentions.members.first();
// Returns <Member>

// Send a Direct Message to a user
message.author.send("hello");
// With Member it works too:
message.member.send("Heya!");

// Mention a user in a message
message.channel.send(`Hello ${user}, and welcome!`);
// or
message.channel.send("Hello " + message.author.toString() + ", and welcome!");

// Restrict a command to a specific user by ID
if (message.content.startsWith(prefix + 'commandname')) {
    if (message.author.id !== 'A user ID') return;
    // Your Command Here
}

// FETCH a member. Useful if an invisible user sends a message.
message.guild.fetchMember(message.author)
  .then(member => {
    // The member is available here.
  });
​
// THIS CHANGES IN DISCORD VERSION 12!!!!!
message.guild.members.fetch(message.author)
  .then(member => {
    // The member is available here.
  });

// Get a Guild by ID
client.guilds.get("the guild id");
// Returns <Guild>

// Get a Channel by ID
client.channels.get("the channel id");
// Returns <Channel>

// Get a Channel by Name
message.guild.channels.find(channel => channel.name === "channel-name");
// returns <Channel>

// Create an invite and send it in the channel
// You can only create an invite from a GuildChannel
// Messages can only be sent to a TextChannel
message.guild.channels.get('<CHANNEL ID>').createInvite().then(invite =>
    message.channel.send(invite.url)
);

const getDefaultChannel = (guild) => {
  // get "original" default channel
  if(guild.channels.has(guild.id))
    return guild.channels.get(guild.id)
​
  // Check for a "general" channel, which is often default chat
  const generalChannel = guild.channels.find(channel => channel.name === "general");
  if (generalChannel)
    return generalChannel;
  // Now we get into the heavy stuff: first channel in order where the bot can speak
  // hold on to your hats!
  return guild.channels
   .filter(c => c.type === "text" &&
     c.permissionsFor(guild.client.user).has("SEND_MESSAGES"))
   .sort((a, b) => a.position - b.position ||
     Long.fromString(a.id).sub(Long.fromString(b.id)).toNumber())
   .first();
}
​
// This is called as, for instance:
client.on("guildMemberAdd", member => {
  const channel = getDefaultChannel(member.guild);
  channel.send(`Welcome ${member} to the server, wooh!`);
});

// Editing a message the bot sent
message.channel.send("Test").then(sentMessage => sentMessage.edit("Blah"));
// message now reads : "Blah"

// Fetching a message by ID (Discord.js versions 9 through 11)
// note: you can line return right before a "dot" in JS, that is valid.
message.channel.fetchMessages({around: "352292052538753025", limit: 1})
  .then(messages => {
    const fetchedMsg = messages.first(); // messages is a collection!)
    // do something with it
    fetchedMsg.edit("This fetched message was edited");
  });
​
// THIS CHANGES IN DISCORD VERSION 12!!!!!
message.channel.messages.fetch({around: "352292052538753025", limit: 1})
  .then(messages => {
    messages.first().edit("This fetched message was edited");
  });