Discord.js // Filtering message startsWith and work around DiscordAPIError for bulkDelete

Question

This is my current code. Credit goes to @André Dion for the help.

  if (message.channel.type == 'text') {
    message.channel.fetchMessages().then(messages => {
        const botMessages = messages.filter(msg => msg.author.bot) 
        message.channel.bulkDelete(botMessages);
        messagesDeleted = botMessages.array().length; // number of messages deleted

        // Logging the number of messages deleted on both the channel and console
        message.channel.send("Deletion of messages successful. Total messages deleted: " + messagesDeleted);
        console.log('Deletion of messages successful. Total messages deleted: ' + messagesDeleted)
    }).catch(err => {
        console.log('Error while doing Bulk Delete');
        console.log(err);
    });
}

When the user enters "!clearMessages" it runs this code and deletes only messages from bots. I would like to add a feature where this also deletes messages from users that starts with !/./> (these messages can be from users not only bots), so I tried editing the line with the const botMessages to this: const botMessages = messages.filter(msg => msg.author.bot && msg.content.startsWith("!" || "." || ">")); but that didn't work. Can you please point out where I'm going wrong and how I can fix this?

Another issue I noticed is that when there is only 1 bot message the bot doesn't delete the message and comes up with an DiscordAPIError, saying that you must provide at least 2-100 messages to delete. Is there a work around this?

Thanks.

Answer 1

There are two issues with const botMessages = messages.filter(msg => msg.author.bot && msg.content.startsWith("!" || "." || ">"));:

1. msg.content.startsWith("!" || "." || ">") is only going to evaluate against the first truthy statement: "!". String#startsWith only takes a single pattern, so you'll have to split that call into three calls. Let's assign the result of these checks into a single variable for convenience:

   const isCommand = msg.content.startsWith("!") || msg.content.startsWith(".") || msg.content.startsWith(">");
   

2. You want to filter out messages that are issued by bot users or that look like a command. Currently your logic is written so that messages that are issued by bots and look like a command are filtered, which is wrong (bots won't be issuing any commands). The correct check with the above additions would be:

   const botMessages = messages.filterArray(msg => {
       const isCommand = msg.content.startsWith("!") || msg.content.startsWith(".") || msg.content.startsWith(">");
   
       return msg.author.bot || isCommand;
   });
   

Correcting your filter logic should fix your DiscordAPIError exception but to ensure no bad calls are being issued, you should guard the bulkDelete invocation:

if (botMessages.length > 1) {
    message.channel.bulkDelete(botMessages);
} else if (botMessages.length) {
    botMessages[0].delete();
} else {
    // nothing to delete
}