Making .env file and modifty codes on discord.js - node.js

Question

Anybody help me on creating .env file and modify the codes!
this is discord.js v12
i cant modify the .env codes on this codes!
but it didnot working
pls help me in this system! and it is yarn installed method!
js file => RushGamerzClient.js
const { Client } = require('discord.js');
module.exports = class RushGamerzClient extends Client {
constructor(options = {}) {
super({
disableMentions: 'everyone'
});
this.validate(options);
this.once('ready', () => {
console.log(`Logged in as ${this.user.username}!`);
});
this.on('message', async (message) => {
const mentionRegex = RegExp(`^<#!${this.user.id}>$`);
const mentionRegexPrefix = RegExp(`^<#!${this.user.id}> `);
if (!message.guild || message.author.bot) return;
if (message.content.match(mentionRegex)) message.channel.send(`My prefix for ${message.guild.name} is \`${this.prefix}\`.`);
const prefix = message.content.match(mentionRegexPrefix) ?
message.content.match(mentionRegexPrefix)[0] : this.prefix;
if (!message.content.startsWith(prefix)) return;
// eslint-disable-next-line no-unused-vars
const [cmd, ...args] = message.content.slice(prefix.length).trim().split(/ +/g);
if (cmd.toLowerCase() === 'hello') {
message.channel.send('Hello!');
}
});
}
validate(options) {
if (typeof options !== 'object') throw new TypeError('Options should be a type of Object.');
if (!options.token) throw new Error('You must pass the token for the client.');
this.token = options.token;
if (!options.prefix) throw new Error('You must pass a prefix for the client.');
if (typeof options.prefix !== 'string') throw new TypeError('Prefix should be a type of String.');
this.prefix = options.prefix;
}
async login(token = this.token) {
super.login(token);
}
};
js file => index.js codes on here
const RushGamerzClient = require('./Structures/RushGamerzClient');
const config = require('../config.json');
const client = new RushGamerzClient(config);
client.login();

Answer 1

You have few options to fix the problem:
Use .env file that has
DISCORD_TOKEN="<your-token>"
then use dotenv (install using npm i -G dotenv) on the top of your file, and login with environment variable
require('dotenv').config();
...
client.login(process.env.DISCORD_TOKEN);