Node.js Asynchronous Readable Stream

async-readable-stream.js

/*
Creating Asynchronous Readable Stream in NodeJS
--------------------------------------------------------

When data is pushed asynchronously to internal buffer, you'll get an asynchronous 
behaviour of the stream. 

See Synchronous Version: https://gist.github.com/hassansin/7f3250d79a386007ce45
*/
var Readable = require("stream").Readable;

function ReadStreamAsync(opts){
  Readable.call(this, opts);
  this._max = 10;
  this._index = 1;
}
require("util").inherits(ReadStreamAsync, Readable)

ReadStreamAsync.prototype._read = function(n) {
  if (this._index > this._max)
    this.push(null);
  else {
    var self = this;
    
    //asynchronously pushing data in internal buffer
    setTimeout(function(){
      var str = '' + self._index++;;
      var buf = new Buffer(str, 'ascii');
      self.push(buf)
    }, 100);
  }
};

console.log(new Date().toTimeString() ,"Start")
var readable = new ReadStreamAsync();

//reading starts from next tick
readable.on('data', function(chunk) {   
    //do stuff
});
readable.on('end', function(){
  console.log(new Date().toTimeString() ,'Done');
});

//scheduled to run on next tick
setImmediate(function(){
  console.log(new Date().toTimeString() ,'setImmediate')
})


/*
Output:
---------

14:55:01 GMT+0000 (UTC) Start
14:55:01 GMT+0000 (UTC) setImmediate
14:55:17 GMT+0000 (UTC) Done


*/