Nested readables

stdin.js

function readOneLine(callback) {

  function readableListener () {
    var chunk = process.stdin.read();
    if (!chunk) return;

    // Let's disconnect our event when we're ready to call back
    process.stdin.removeListener('readable', readableListener);

    // Attempt 1:
    // Not pausing or ending, will run all 3 readers, but expect
    // one more extraneous line
    //

    // Attempt 2:
    // pause() here will not let 'Second' reader run and just exit the process
    // process.stdin.pause();

    // Attempt 3:
    // Removing the listener, and then checking if any listeners were added
    // "later," makes 'Third' fail to run and just exit the process
    // setImmediate(function () {
    //   if (require('events').EventEmitter.listenerCount(process.stdin, 'readable') === 0) {
    //     process.stdin.pause();
    //   };
    // })

    return callback(null, chunk.toString());
  }

  process.stdin.on('readable', readableListener);
}

// First
process.stdout.write('First: ');
readOneLine(function (err, data) {
  console.log('Got data from First:' + data);

  // Second
  process.stdout.write('Second: ');
  readOneLine(function (err, data) {
    console.log('Got data from Second:' + data);

    // Third
    setTimeout(function () {
      process.stdout.write('Third: ');
      readOneLine(function (err, data) {
        console.log('Got data from Third:' + data);
      });
    }, 100);

  });

});