Injecting records into the output stream? about node-csv HOT 4 CLOSED

Hi, not completly sure i understand your need but i've just commited a write (and end) function that might help you. With those method, you can manually inject new data (string, array and object) to be writen to the output stream. u can look at 'test/write.js' for exemples and let me know if that help.

from node-csv.

David,

Thanks for that. I can see how that would be useful for writing a new stream of records.

My requirement is to progressively inject additional records as the input stream is parsed. I think the neatest way to model it would be to add 'beforeData' and 'afterData' events that are passed a function that can be called to write one or more records, and perhaps a parameter that indicates the number of records written.

These events would be emitted before and after the data event is emitted so that the additional records could be injected into the output stream before and after records read from the input stream.

The idea is to allow additional progressive summary or analysis records to be written into the output stream as the input stream is processed. So, for example, every 10 records in the input stream might be summarised by an 11th record in the output stream.

from node-csv.

you should be able to achieve this inside the transform method. if i remember well, this method has an interesting property which is to bypass a line if it return null while at the same time you could call the new write method, for exemple:

var test = csv()
.transform(function(data, index){
test.write([ index, data[0]--, 'and '+data[1] ]);
test.write([ index, data[0]++, 'or '+data[1] ]);
})

Would that work?

from node-csv.

Yes, I think that works for my purposes.

I have added an example which shows how to use this technique to duplicate the header line before each output line.

from node-csv.