ytdl：“url”参数必须是字符串类型。 接收类型未定义

Question

I'm working on a Discord bot using Discord.js and ytdl. However, whenever I type ?play and my play command is executed, this error is thrown:

 (node:15840) UnhandledPromiseRejectionWarning: TypeError [ERR_INVALID_ARG_TYPE]: The "url" argument must be of type string. Received type undefined at URL.parse(url.js:154:11) at Object.urlParse [as parse] (url.js:148:13) at Object.exports.getURLVideoID (C:\\Users\\MauSc\\Desktop\\[MENU DOCS] Bot\\node_modules\\ytdl-core\\lib\\util.js:273:22) at Function.exports.validateURL(C:\\Users\\MauSc\\Desktop\\[MENU DOCS] Bot\\node_modules\\ytdl-core\\lib\\util.js:328:20) at Object.module.exports.run (C:\\Users\\MauSc\\Desktop\\[MENU DOCS] Bot\\commands\\play.js:18:22) at Client.bot.on (C:\\Users\\MauSc\\Desktop\\[Menu DOCS] Bot\\index.js:51:38) at Client.emit (events.js:198:13) at MessageCreateHandler.handle (C:\\Users\\MauSc\\Desktop\\[MENU DOCS] Bot\\node_modules\\discord.js\\src\\client\\websocket\\packets\\handlers\\MessageCreate.js:9:34) at WebSocketPacketManager.handle (C:\\Users\\MauSc\\Desktop\\[MENU DOCS] Bot\\node_modules\\discord.js\\src\\client\\websocket\\packets\\WebSocketPacketManager.js:105:65) at WebSocketConnection.onPacket (C:\\Users\\MauSc\\Desktop\\[MENU DOCS] Bot\\node_modules\\discord.js\\src\\client\\websocket\\WebSocketConnection.js:333:35) (node:15840) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1) (node:15840) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

The code is all copied from another bot I made, so I'm not sure why the error suddenly appears.

This is the code:

const Discord = require("discord.js");
const ytdl = require('ytdl-core');
const streamOptions ={
    seek: 0,
    volume: 1
}

const bot = new Discord.Client({disableEveryone: true});

var musicUrls = [];

bot.on("message", async message => {

module.exports.run = async (bot, message, args) => {
             let url = args[1];
             let voiceChannel = message.guild.channels.find(channel => channel.name === 'Musik Bot');

             if(ytdl.validateURL(url))
             {
                console.log("Valid URL");
                var flag = musicUrls.some(element => element === url);
                if(!flag)
                {
                    musicUrls.push(url);
                    if(voiceChannel != null)
                    {

                        if(voiceChannel.connection)
                        {
                            console.log("Connection exists");
                            const embed = new Discord.RichEmbed();
                            embed.setAuthor(bot.user.username, bot.user.displayAvatarURL);
                            embed.setDescription("Du hast erfolgreich einen Track zu der Playlist hinzugefügt!");
                            message.channel.send(embed);
                        }
                        else {
                            try {
                                const voiceConnection = await voiceChannel.join();
                                await playSong(message.channel, voiceConnection, voiceChannel);
                            }
                            catch(ex)
                            {
                                console.log(ex);
                             }
                         }
                    }

                 }
             }
}
     async function playSong(messageChannel, voiceConnection, voiceChannel)
{
    const stream = ytdl(musicUrls[0], { filter : 'audioonly'});
    const dispatcher = voiceConnection.playStream(stream, streamOptions);

    dispatcher.on('end', () => {
        musicUrls.shift();

        if(musicUrls.length == 0)
            voiceChannel.leave();
        else
        {
            setTimeout(() => {
                 playSong(messageChannel, voiceConnection, voiceChannel);
            }, 1000);
        }
    });
    try {
        if(!message.content.startsWith(prefix)) return;
        let commandfile = bot.commands.get(cmd.slice(prefix.length)) || bot.commands.get(bot.aliases.get(cmd.slice(prefix.length)))
        console.log(commandfile);
        if (commandfile) commandfile.run(bot, message, args)
    } catch (error) {
        console.error(error);
    }
}},


module.exports.config = {
    name: "play",
    aliases: []
});

Answer 1

args[1] is undefined when your code is run, which means it was never provided. This causes url to also be undefined, and your error is then thrown from ytdl because validateURL() expected a string.

Before continuing with the command, ensure that the required argument is present. If not, return an error message. For example...

if (!args[1]) {
  return message.channel.send('You must provide a URL!')
    .catch(console.error);
}