node.jsstream

How to compose transform Streams in node.js

I have a csv parser implemented as a series of transform streams:

process.stdin
    .pipe(iconv.decodeStream('win1252'))
    .pipe(csv.parse())
    .pipe(buildObject())
    .pipe(process.stdout);

I'd like to abstract the parser (in its own module) and be able to do:

process.stdin.
    .pipe(parser)
    .pipe(process.stdout);

where parser is just the composition of the previously used transform streams.

If I do 

var parser = iconv.decodeStream('win1252')
    .pipe(csv.parse())
    .pipe(buildObject());

then parser is set to the buildObject() stream and only this transformation stream receives the data.

If I do 

var parser = iconv.decodeStream('win1252');
parser
    .pipe(csv.parse())
    .pipe(buildObject());

it doesn't work either, as .pipe(process.stdout) will be called on the 1st transform stream and the 2 others will be bypassed.

Any recommendation for an elegant composition of streams?

Solution

  • Unfortunately, there is no built-in way to do that, but there is cool multipipe package. Use like this:

    var multipipe = require('multipipe');

var parser = multipipe(iconv.decodeStream('win1252'), csv.parse(), buildObject());