and-stream

Node.js Stream to filter multiple-streams of incoming objects, and only return objects that are present in ALL streams.

Installation

Install via npm:

$ npm install and-stream

Examples

Only print out objects that are present in two input object streams

var andStream = require('and-stream');
 
// No key passed into the factory method, so just uses JSON.stringify for uniqueness
var and = andStream();
and
  .on('data', console.log)
  .on('end', process.exit);
 
aStreamOfObjects()       // emits objects
  .pipe(and.stream());
 
anotherStreamOfObjects() // emits objects
  .pipe(and.stream());
 
// Only objects that are identical and emitted by both streams will be printed
 

The and-stream constructor takes an optional argument which is used to determine the unique key to identify an object by. If not used, it will default to using JSON.stringify to uniquely identify each object, so only if the exact same object is present on all streams will the objected be emmitted by the and-stream.

Use the name property on the object as the object key

var andStream = require('and-stream');
 
// Use the 'name' field as the key for anding object streams
var and = andStream('name');
and
  .on('data', console.log)
  .on('end', process.exit);
 
aStreamOfObjects()       // emits objects
  .pipe(and.stream());
 
anotherStreamOfObjects() // emits objects
  .pipe(and.stream());
 
// Only objects that have the same .name field on both streams will be printed
 

Use a custom function on the objects to determine the key

var andStream = require('and-stream');
 
// Use the 'name' field as the key for anding object streams
var and = andStream(function (data) {
  var strKey = data.name;
  var useKey = new Buffer(strKey, 'utf8').toString('base64');
  return useKey;
});
and
  .on('data', console.log)
  .on('end', process.exit);
 
aStreamOfObjects()       // emits objects
  .pipe(and.stream());
 
anotherStreamOfObjects() // emits objects
  .pipe(and.stream());
 
// Only objects that have the same base64 of the .name field on both streams will be printed