How to use stream - 10 common examples

let buildStream = (key) => {
      let stream = new Writable;

      // $FlowFixMe: TODO add to flow definition
      stream.columns = 1000;

      // $FlowFixMe: TODO ditto
      stream.write = (msg) => {
        stream.emit("data", msg);
        data[key] += msg;
      };

      return stream;
    };

const buildStream = (key): Writable => {
      const stream = new Writable();

      // $FlowFixMe: TODO add to flow definition
      stream.columns = 1000;

      // $FlowFixMe: TODO ditto
      stream.write = msg => {
        stream.emit('data', msg);
        data[key] += msg;
      };

      return stream;
    };

function Aggregate(collection, options) {
  if (!(this instanceof Aggregate)) return new Aggregate(collection, options)

  // readable mode for streaming the cursor
  Readable.call(this, {
    objectMode: true
  })

  this.collection = collection
  this.options = options = options || {}
  this.pipeline = []
}

function InputStream(source, options) {
  if (!(this instanceof InputStream))
    return new InputStream(source, options);

  Readable.call(this, options);

  options = options || { highWaterMark: 16 * 1024 }; 

  // source is a winrt iinputstream, such as a socket or file
  this._source = source;
  this._buffer = new Buffer(options.highWaterMark);
}

function Query(collection, options) {
  if (!(this instanceof Query)) return new Query(collection, options)

  Readable.call(this, {
    objectMode: true
  })

  this.collection = collection
  this.criteria = {}
  this.document = {}
  this.options = options || {}
  // which type of .then() is set
  this._then = 'query'
}

let buildStream = (key) => {
      let stream = new Writable;
      stream.columns = 1000;
      stream.write = (msg) => {
        stream.emit("data", msg);
        data[key] += msg;
      };
      return stream;
    };

function createReadableStreamFromString(s) {
	const readable = new stream.Readable();
	readable._read = function () {};
	readable.push(s);
	readable.push(null);
	return readable;
}

const Writable = cb => {
  const writable = new Stream.Writable({ objectMode: true })
  writable._write = (chunk, _, done) => {
    assert.strictEqual(chunk, 'A')
    done()
    cb && cb()
  }
  return writable
}

function createMockWriteStream () {
  const s = new Stream.Writable()
  s._data = ''
  s._write = function (chunk, encoding, done) {
    s._data += chunk.toString()
    done()
  }
  return s
}

function send(options, data, encoding, contentType) {
  options.headers  = {'Content-Type' : contentType};
  options.encoding = encoding;

  return _send(options, data, new PassThrough()).pipe(request(options, handler));
}