index.js

#!/usr/bin/env node  //this line is to access app any where in your teminal by writing 'watchit' and then the file path you want to watch

const chokidar = require("chokidar");
const debounce = require("lodash.debounce");
const program = require("caporal");
const fs = require("fs");
const { spawn } = require('child_process');
const chalk = require('chalk')

program
    .version('0.0.1')
    .argument('[filename]', 'Name of a file to execute')
    .action(async ({ filename }) => {
        const name = filename || 'index.js';

        try{
            await fs.promises.access(name);
        } catch{
            throw new Error(`Could not find the file '${name}'`)
        }
        
        let proc;
        const start = debounce(() => {
            if(proc){
                proc.kill();
            }
            console.log(chalk.blue('>>>> Starting process...'));
            proc = spawn('node', [name], { stdio : 'inherit' });
        }, 500);

        chokidar.watch('.')
            .on("add", start)
            .on("change", start)
            .on("unlink", start);
    
    });

program.parse(process.argv);

//use ' watchit help ' on your terminal to see more informations