ostream.js

var path = require('path'),
    fs = require('fs');

var filepath = path.join(__dirname, 'write.txt');
var writeStream = fs.createWriteStream(filepath);

writeStream.write('Hello World!');
writeStream.end();

writeStream.on('error', function(err){
  console.log('An error occured');
  console.log(err);
});

writeStream.on('close', function(){
  console.log('writable stream closed');
});