Discord.JS UnhandledPromiseRejectionWarning：TypeError：无法读取未定义的属性“startsWith”

Question

I'm currently trying to implement speech recognition into a discord bot, but I keep running into errors. I'm also new to Discord.JS and programming as a whole.

I copied some of the following code from an event file that interprets normal messages instead of speech, and it works fine there.

The following line throws an "UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'startsWith' of undefined": if (!msg.content.startsWith(prefix) || msg.author.bot) return;

My entire file:

const fs = require('fs');

module.exports = {
    name: "join",
    description: "Joins the VC that user is in",
    async execute(client, message, args, Discord) {
        const voiceChannel = message.member.voice.channel;
        const connection = await voiceChannel.join();

        if (!voiceChannel) return message.channel.send('Join a VC retard');
        const permissions = voiceChannel.permissionsFor(message.client.user);
        if (!permissions.has('CONNECT')) return message.channel.send("You don't have the correct permissions");
        if (!permissions.has('SPEAK')) return message.channel.send("You don't have the correct permissions");

        connection.client.on('speech', msg => {
            console.log(msg.content);
            const prefix = 'yo bot ' || 'Aries ' || 'Ares ' || 'yobot ';
            if (!msg.content.startsWith(prefix) || msg.author.bot) return;

            const args = msg.content.slice(prefix.length).split(/ +/);
            const cmd = args.shift().toLowerCase();

            const command = client.commands.get(cmd);

            if (command) command.execute(client, msg, args, Discord);
        })
    }
} 

Answer 1

If message content is not a string then you cannot use that function.

You need to check if message content exists first:

if (!msg.content 
    || !msg.content.startsWith(prefix)
    || msg.author.bot
   ) {...}

Answer 2

You need to make sure that the message content is defined, before reading it's startsWith property. You can do this with optional chaining .

if (!msg?.content?.startsWith(prefix) || msg.author.bot) return;

msg?.content?.startWith(prefix) will return undefined if either:

• msg does not have a content propery
• content does not have a startWith property