JavaScript 错误：TypeError：无法读取未定义的属性“设置”

Question

我正在使用 Visual Studio Code 编写代码，然后当我执行代码时，出现此错误：“TypeError: Cannot read property 'set' of undefined”

这是完整的代码：

const Discord = require('discord.js');
const client = new Discord.Client();
const prefix = 'm!';
const fs = require('fs');

client.command = new Discord.Collection();

const commandFiles = fs.readdirSync('./commands/').filter(file => file.endsWith('.js'));
for(const file of commandFiles){
    const command = require(`./commands/${file}`);

    client.commands.set(command.name, commad)
}

client.once('ready', () => {
    console.log('Bot is online!');
});

client.on('message', message => {
    if (!message.content.startsWith(prefix) || message.author.bot) return;

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

    if(command === 'ping'){
        client.command.get('ping').execute(message, args);
    }
});