Trying to learn module.exports but having some problem - node.js

Question

I'm using discord.js from some week and now I would like to do that when someone enter in a vocal chat, the bot will send a message in the console. I tried using this code in the main file of the bot and perfectly worked but when I try to put it in another file and export it in the main file it doesn't work. Someone that can help me and maybe explain it?
main.js:
const Discord = require('discord.js');
const fs = require("fs");
const client = new Discord.Client();
const { prefix, token } = require("../config.json");
client.commands = 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, command);
}
const a = require("./commands/test1")
if(client.guilds.cache.get("<guild if>")){
return a
}
test1.js:
const Discord = require('discord.js');
const fs = require("fs");
const client = new Discord.Client();
const { prefix, token } = require("../config.json");
module.exports = {
execute() {
client.on('voiceStateUpdate', (oldState, newState) => {
if (newState.channelID === null) console.log('Inside channel', oldState.channelID);
else if (oldState.channelID === null) console.log('Outside channel', newState.channelID);
else console.log('user moved channels', oldState.channelID, newState.channelID);
})}}

Answer 1

In this part in your main.js file:
const a = require("./commands/test1")
if(client.guilds.cache.get("<guild if>")){
return a
}
The a variable contains an object like { execute: function(){...} }. You not calling the execute function.
Try this:
const { execute } = require("./commands/test1")
if(client.guilds.cache.get("<guild if>")){
return execute();
}

Answer 2

Can you try adding the keyword function before the word execute()?
Alternatively, you could do:
// \/ you can put arguments here
module.exports.execute = () => {
// function here
}
and then in your index file..
const a = require("./commands/test1")
if(client.guilds.cache.get("<guild if>")){
return a.execute(this is where you would put your arguments)
}
Happy coding!