Why is there an error called 'send' of undefined?

Question

Why is there an error called 'send' of undefined?

에라 모르겠다 한글로 써야지.

Error: Cannot read property 'send' of undefined 이런 오류가 왜 날까요?

MY CODE:

const discord = require('discord.js')
const client = new discord.Client()
const { prefix, token } = require("./config.json")
console.log("켜짐")

client.on('ready', () =>{
    client.user.setActivity(",help")
})

client.on('message', (message) =>{



    if(message.author.bot) return;

    if(!message.content.startsWith(prefix)) return

    else if(message.content.startsWith(`${prefix}help`)) {
        const embed = new discord.MessageEmbed()
        .setColor(`#adsjk2`)
        .setDescription("도움말")
    message.channel.send(embed)
    } 
    
})
client.on('guildMemberAdd', (member) => {
    const welcomeChannel = member.guild.channels.cache.find(channel => channel.topic === '#welcome')
    if(!welcomeChannel) return
    
    if(welcomeChannel) {
    welcomeChannel.send(`<@${member.id}>님 환영합니다!`)
    return
    } else {
        return undefined
    }


})
client.on('guildMemberRemove', (member) =>{
    const welcomeChannel = member.guild.channels.cache.find(channel => channel.name === 'welcome')

    welcomeChannel.send(`<@${member.id}>님이 나가셨습니다...`)
    return
})
client.login(token) 

Error: Cannot read property 'send' of undefined

Answer 1

I think you are having the problem here,

const welcomeChannel = member.guild.channels.cache.find(channel => channel.topic === '#welcome')

change this to,

const welcomeChannel = member.guild.channels.cache.find(channel => channel.name === 'welcome')

in this I changed channel.topic to channel.name

this should work

I think this was the line you was having the error with as you didn't tell me the line specifically