无法读取未定义的属性“名称”

Question

I've been getting an error along the lines of "Cannot read property 'name' of undefined" and the error traces back to this code

const roleName = message.guild.roles.cache.find(r => (r.name === args[1].toString()) || (r.id === args[1].toString().replace(/[^\w\s]/gi, '')));

What's going wrong here?

slightly larger peice of code

if (!message.member.hasPermission('MANAGE_ROLES')) return message.channel.send(`You do not have MANAGE_ROLES permission`)
try {
    const user = message.mentions.users.first();
    const member = message.guild.member(user);
    const roleName = message.guild.roles.cache.find(r => (r.name === args[1].toString()) || (r.id === args[1].toString().replace(/[^\w\s]/gi, '')));
    //after this i create a discord embed, give the member the role specified then send the embed.
} catch (err) {
    console.log(err)
}

Answer 1

Add an Elvis operator:

const roleName = message.guild.roles.cache.find(r => 
  (r?.name === args[1].toString()) 
  || (r?.id === args[1].toString().replace(/[^\w\s]/gi, ''))
);

Or do it the old way:

const roleName = message.guild.roles.cache.find(r => 
  r 
  && (r.name === args[1].toString()) 
  || (r.id === args[1].toString().replace(/[^\w\s]/gi, ''))
);

Answer 2

So you're getting this error because you're trying to access 'r.name' in your Array.find() method and some of the entries in the array appear to be 'undefined' or 'null'. I would first run an Array.filter(r => !!r) and then chain on the .find() method afterwards to make sure all your entries are not undefined/null.