read two file names from user and append contents of first file into second file .

var express = require("express");
const bodyParser = require("body-parser");
var fs = require("fs");
var buf = new Buffer(1024);

var app = express();
app.use(bodyParser.urlencoded({
extended: true
}));
app.use(bodyParser.json());
app.get("/", function(request, response){
response.writeHead(200,{'content-type':'text/html'});
response.write('<form name="file_input" method="post">');
response.write('<h1> Select 2 files to append File1 Contents to File2 </h1>');
response.write('<input type="file" name="file1"><br>');
response.write('<input type="file" name="file2"><br>');
response.write('<input type="submit"><br>');
response.write('</form>');
response.end();
});

app.post('/', (req, res) => {
const file1 = req.body.file1;
const file2 = req.body.file2;
fs.open(file1, 'r+', function(err, fd) {
if (err) {
return console.error(err);
}
console.log("File open successfully");
fs.read(fd, buf, 0, buf.length, 0, function(err, bytes){
if (err){
console.log(err);
}
var data =buf.toString();
fs.appendFile(file2, data, (err) => {
if (err) {
console.log(err);
}
else {
console.log("\nFile Contents are appended successfully");
res.write('File 1 contents are appended in file 2');
}
});
});
});
res.end();
})
app.listen(8080);
console.log("Server is running at http://localhost:8080");