Question

In my module.js I have

var Stream = require('stream');

module.exports = function () {
  var stream = new Stream();

  stream.readable = true;

  stream.emit('data', 'some stuff')
  stream.emit('end')

  return stream;
}

and in my index.js

var module = require('./module')

module().pipe(process.stdout)

substack’s example from the stream handbook is working just fine. Why doesn’t my code show anything in the command line?

Answer 1

Because you are emitting data before calling pipe, and ‘data’ listener is attached after first ‘data’ event is fired

EventEmitter’s calls are synchronous (as almost everything else non-IO in node.js)

A bit simplified version of

stream.emit('data', 'some stuff')
stream.pipe(process.stdout)

without EventEmitter could be rewritten as

stream.listeners = [];
// 'emit' call
var ondata = stream.listeners.data;
if (ondata) {
   // only one listener case in the example
   ondata('some stuff');
}
// 'pipe' call
stream.listeners.data = function(buff) {
    process.write(buff);
}