11-fs-async.js

const { readFile, writeFile } =  require('fs')

readFile('./content/first.txt','utf8', (err,result)=>{
    if(err){                //without utf8 onlu buffer can occur
        console.log(err)
        return
    }
    const first = result;
    readFile('./content/second.txt','utf8',(err,result)=>{
        if(err){                //without utf8 onlu buffer can occur
            console.log(err)
            return
        }
        const second = result;
        writeFile('./content/result-async.txt',
            `Here is the result : ${first}, ${second}`
            ,(err,result)=>{
                if(err){
                    console.log(err)
                    return
                }
                console.log('done with this task');
            })
    })
})
console.log('starting next task');