Discord.js On message command not working

Question

Discord.js Problem I should point out I am not experienced at discord.js. I have the following code which is supposed to change the users requested sum or expression into the actual answer and message back. My other command is working but not the other here is the code for that:

client.once("message", msg => {
    if(msg.content.includes("!simple")){
       math = Number(msg.content.slice(msg.content.search("e")))
msg.reply(guild.username + "The answer is " + math )


    }
})

I basically remove the command part via slice method then compute the value of it using the Number function and subsequently return it but I get no response from the bot. Any help appreciated

Answer 1

In the mean while Discord changed their APIs. client.on("message") is deprecated now. The working example at 2021 would look like this:

const { Client, Intents } = require('discord.js');
const client = new Client({ intents: [Intents.FLAGS.GUILDS, Intents.FLAGS.GUILD_MESSAGES] });

client.on("messageCreate", (message) => {
  if (message.author.bot) return false; 
  
  console.log(`Message from ${message.author.username}: ${message.content}`);
});

client.login(process.env.BOT_TOKEN);

The boot needs explicit permission to read messages. If the bot doesn't have that permission then the on messageCreate event will not be fired.

Answer 2

i'm not to sure about what you mean with "requested sum or expression", something like this?

client.on('message', msg => {
  if (msg.content.startsWith('!simple')) {
    var tocalc = msg.content.substr(8);
    if (!tocalc.match(/^[\d\(\)\+\-\/\*e\.%=!\s]+$/)) { // allowed = ['number', '(', ')', '+', '-', '*', '/', 'e', '.', '%', '=', '!', ' ']
        msg.reply('no valid expression or calculation');
        return;
    }
    var result;
    try {
        result = Function('return ' + tocalc)();
    } catch(e) {
        console.error(`tried to exploit! ban user ${msg.author.id}!`);
        return;
    }
    if (isNaN(result)) {
        console.error(`tried to exploit! ban user ${msg.author.id}!`);
        return;
    }
    msg.reply(result);
  }
});

!simple 1 + 8 - (4 * .25) // 8
!simple 1 == 1 // true
!simple 9 % 2 != 8 % 2 // true