Read Write and appent a mode

 //create file if file is not create then create other open

//read old data
//insert new data
//read all data


let fs=require("fs");


//create file if file is not create then create other open
console.log("Step1");
fs.open('tejas.txt','a+',function (error,data) {

    //error
    if(error){
        console.log(`Something is wrong for open file :${error}`);
        return;
    }

    //read
    console.log("Step2---print old data");
    const buffer = Buffer.alloc(1024);
    fs.read(data, buffer, 0, buffer.length, 0, function(err, bytesRead) {
        if (err) {
            console.error('Error reading file.');
            return;
        }

        if (bytesRead > 0) {
            console.log(buffer.toString('utf8', 0, bytesRead));
        }

    });


    //insert new data
    console.log("Step3---New data append");
    fs.appendFile(data," tttttt This is new append data",function (error,data) {

    })
    // Read
    console.log("Step4---Old data + new data");
    fs.read(data, buffer, 0, buffer.length, 0, function(err, bytesRead) {
        if (err) {
            console.error('Error reading file.');
            return;
        }

        if (bytesRead > 0) {
            console.log('File Contents:\n' + buffer.toString('utf8', 0, bytesRead));
        }

    });

});