blacklist

client.on('message', async message => {
    if (!message.content.startsWith(prefix) || message.author.bot) return;
const args = message.content.slice(prefix.length).trim().split(/ +/);
const command = args.shift().toLowerCase();
let user = message.mentions.members.first() || client.users.cache.find(u => u.id === args[0])
  let member = message.guild.member(user)
if(command === "blacklist") {
    if(!message.member.hasPermission("MANAGE_GUILD")) return;
  if(!user) return message.channel.send('i cant find this user!')
  if(db.has(`u`,member.id)) return message.channel.send('this member already blacklisted!')
  db.set(`u`,member.id)
  message.channel.send('member added to blacklisted users!')
}
if(command === "remove-blacklist") {
    if(!message.member.hasPermission("MANAGE_GUILD")) return;
    if(!user) return message.channel.send('i cant find this user!')
    if(!db.has(`u`,member.id)) return message.channel.send('this member not blacklisted!')
    db.delete(`u`,member.id)
    message.channel.send('member removed from blacklisted users!')
}
if(command === 'delete-all') {
    if(!message.member.hasPermission("MANAGE_GUILD")) return;
    db.delete('u')
    message.channel.send('removed all blacklists')
}
});

السطر اللي تحطه في كل اكوادك
if(db.has("u", message.author.id)) return message.channel.send('you are blacklisted!')