How to create a DiscordJS Invite Tracker

1ready.js

// Welcome to my gist! This is how you can create an invite tracker using JavaScript and Discord.JS!
// First we are going to statt off in our ready event.

// Create a new Collection called guildInvites and add it to your client
// client is the new Client you created in your main file. If you're using an event handler, make sure to pass the client into this file.
const { Collection } = require("discord.js");

// Collection is an enhanced Map which we are going to save our invites to.
const guildInvites = new Collection();
client.invites = guildInvites;

// Next, we are going to fetch invites for every guild and add them to our map.
for(const guild of client.guilds.cache.values()) {
  // Here we are getting all invites for the guild
  // Using our client.invites collection we created, we are saving all invites to the cache by guild id.
  guild.fetchInvites()
  .then(invite => client.invites.set(guild.id, invite)
  .catch(error => console.log(error));
};
  
// Now we can move to our inviteCreate event.

2inviteCreate.js

// We are going to add our new invite to the cache every time a new one is created.
// This is to ensure we always have a valid cache.
// Out inviteCreate event passes a parameter, which we call "invite" in this example.
// We can also use our client.invites collection we created in our ready event.

client.invites.set(invite.guild.id, await invite.guild.fetchInvites());
// invite has a guild property that we can access the guild from.
// Note here that we require an async function to fetchInvites. Otherwise use a .then()

// Let us move on to our guildMemberAdd event

3guildMemberAdd.js

// Our guildMemberAdd event passes a parameter we called "member"
// Firstly, lets make sure this is not a bot. We simply do not care about them.
if(member.user.bot) return;

// Now we want to get all invites from our client.invites cache.
// Our member variable has a guild property we can use to get the guild.
const cachedInvites = client.invites.get(member.guild.id)

// Now we want to get any new invites that may have been created and add them to our map.
// Note, we are using await meaning you'll need an async function. Otherwise use .then()
const newInvites = await member.guild.fetchInvites();
client.invites.set(member.guild.id, newInvites);

// Now in DiscordJS there isn't a way to see who used an invite.
// Due to this, we will track their uses to see which invite updates.
// We are going to find an invite in our cache that has a smaller amount of uses than it's previous cache amount.
const usedInvite = newInvites.find(invite => cachedInvites.get(invite.code).uses < invite.uses);

// Now we can send an embed to the logging channel of your choice.
// Lets get the MessageEmbed constructor from the discordjs package.
const { MessageEmbed } = require("discord.js");

// Now lets find the logging channel in the current guild.
const logChannel = member.guild.channels.cache.find(channel => channel.name === "logs");
// If the channel doesn't exist, lets do nothing.

if(!logChannel) return;

// We can now use our usedInvites variable to access different information about the invite.
// To simplify this into one line, we can do this:
const { code, uses, inviter, channel } = usedInvites;

// Now lets construct an embed.
const embed = new MessageEmbed()
        // We can put the member's tag and avatar in the title.
        .setAuthor(`${member.user.tag} joined!`, member.user.displayAvatarURL())
        // Here we create a field and use an array to join the description by a newline. 
        .addField("Information", [
                `➤ **Code:** ${code}`,
                `  ➤ **Created by:** ${inviter.tag}`,
                `  ➤ **Uses:** ${uses}`,
                `➤ **Channel:** ${channel}`
            ].join('\n'))
                  // And we can set our embed color to BLUE so it doesn't look plain.
                .setColor("BLUE");

// Finally, lets send the embed to our log channel.
logChannel.send(embed);  
// Now we're done!