javascript - How do I stream response in express?

Question

I've been trying to get a express app to send the response as stream.

var Readable = require('stream').Readable;
var rs = Readable();


app.get('/report', function(req,res) {
    
    res.statusCode = 200;
    res.setHeader('Content-type', 'application/csv');
    res.setHeader('Access-Control-Allow-Origin', '*');

    // Header to force download
    res.setHeader('Content-disposition', 'attachment; filename=Report.csv');

    
    rs.pipe(res);

    rs.push("USERID,NAME,FBID,ACCOUNT,SUBSCRIPTION,PRICE,STATE,TIMEPERIOD
");

    for (var i = 0; i < 10; i++) {
        rs.push("23,John Doe,1234,500,SUBSCRIPITON,100,ACTIVE,30
");
    }

    rs.push(null);
});      

It does print in the console when I replace "rs.pipe(res)" by "rs.pipe(process.stdout)". But how to make it work in an express app?

Error: not implemented
    at Readable._read (_stream_readable.js:465:22)
    at Readable.read (_stream_readable.js:341:10)
    at Readable.on (_stream_readable.js:720:14)
    at Readable.pipe (_stream_readable.js:575:10)
    at line "rs.pipe(res);"

Answer 1

You don't need a readable stream instance, just use res.write():

res.write("USERID,NAME,FBID,ACCOUNT,SUBSCRIPTION,PRICE,STATE,TIMEPERIOD
");

for (var i = 0; i < 10; i++) {
    res.write("23,John Doe,1234,500,SUBSCRIPITON,100,ACTIVE,30
");
}

res.end();

This works because in Express, res is based on Node's own http.serverResponse, so it inherits all its methods (like write).