streams

streams.js

const stream = require('stream');

let readable = new stream.Readable({
    objectMode: true,
    read: function() {
        let arr = [ { a: 1 }, { b: 1 }, { c: 1 } ];
        arr.forEach( item => { this.push(item) });
        this.push(null);
    }
}).on('end', function() {
    console.log('Done reading');
});

let transform = new stream.Transform({
    objectMode: true,
    transform: function( chunk, encoding, next ) {
        chunk.lol = true;
        this.push(chunk);            
        next();
    },
    flush: function(done) {
        done();
    }
}).on('end', function() {
    console.log('Done transforming');
});

let writable = new stream.Writable({
    objectMode: true,
    write: function( chunk, encoding, next ) {
        console.log(chunk);
        next();
    }        
}).on('finish', function() {
    console.log('Done writing');
});

readable.pipe(transform).pipe(writable);

Note that the writable-stream emits «finish» instead of «end».