transfuse

Streaming JSON transformer.

examples

synchronous transform

var transfuse = require('transfuse');

var tr = transfuse(function (doc) {
    return { x : doc.a || doc.b };
});

process.stdin.pipe(tr);
tr.pipe(process.stdout);
process.stdin.resume();

output:

$ echo '[{"a":3},{"b":5},{"a":10,"b":3},{"b":55,"c":6}]' | node example/sync.js 
[
{"x":3}
,
{"x":5}
,
{"x":10}
,
{"x":55}
]

asynchronous transform

var transfuse = require('transfuse');

var tr = transfuse(function (doc, map) {
    map({ x : doc.a || doc.b });
});

process.stdin.pipe(tr);
tr.pipe(process.stdout);
process.stdin.resume();

output:

$ echo '[{"a":3},{"b":5},{"a":10,"b":3},{"b":55,"c":6}]' | node example/async.js 
[
{"x":3}
,
{"x":5}
,
{"x":10}
,
{"x":55}
]

transforming at key paths

var transfuse = require('transfuse');
var tr = transfuse(['rows', /./, 'c'], function (doc, map) {
    doc.pizza = "tacos"
    map(doc);
});
tr.pipe(process.stdout);

var stream = new(require('net').Stream);
stream.pipe(tr);

stream.emit('data', JSON.stringify({
    rows : [
        { a : 3, c : {} },
        { a : 4, c : { cats : 'dogs' } },
        { a : 2, c : { beep : 'boop' } },
    ],
    bling : 'blong',
}));
stream.emit('end');

methods

var transfuse = require('transfuse');

transfuse(keyPath=[/./], fn)

Return a readable/writable stream transforming an incoming JSON stream of "data" events into an outgoing stream of "data" events with fn.

If fn.length === 1 use transfuse.sync. Otherwise use transfuse.async.

If fn is a string then it should contain a function body which will be run with vm.runInNewContext.

The optional keyPath argument can be used to transform a specific nested section of the document. See JSONStream for how key path Arrays work.

transfuse.sync(fn)

Return a readable/writable stream to transform using fn(doc), which should return the new document to insert.

transfuse.async(fn)

Return a readable/writable stream to transform using fn(doc, map), which should call map with the new document value.

The order of the resulting collection will depend on the order in which the map(doc) functions fired.

install

With npm do:

npm install transfuse

license

MIT/X11