Streams and event loop - do data handlers always fire on next tick?

Question

Say I have a readable stream, like so:

const strm = fs.createReadStream(file);
strm.on('data', function onData(d){});

my question is, does the onData callback fire in the next tick of the event loop? Or is it possible for the onData handler to be called twice in the same tick of the event loop?

score 1 · Accepted Answer · answered May 01 '18 at 01:52

The data handlers can fire multiple times in the same tick of the event loop, see:

https://github.com/nodejs/help/issues/1222

Yes:

const stream = require('stream'); 
const readable = new stream.Readable({read(){}}); 
readable.on('data', () => console.log('data')); 
process.nextTick(() => console.log('next tick'));
readable.push('foo'); 
readable.push('foo');

Output:

data data next tick

Streams and event loop - do data handlers always fire on next tick?

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