How do I test if a stream has ended?

Question

I have a stream that may or may not have already ended. If it has ended, I don't want to sit there forever waiting for the end event. How do I check?

Answer 1

As of node 12.9.0, readable streams have a readableEnded property you can check – see readable.readableEnded in the Stream documentation.

(Writable streams have a corresponding property)

Answer 2

If you absolutely have to, you can check stream._readableState.ended, at least in node 0.10 and 0.12. This isn't public API though so be careful. Also apparently all streams aren't guarantee to have this property too:

Worth reading on this:

https://github.com/hapijs/hapi/issues/2368

https://github.com/nodejs/node/issues/445

Answer 3

You probably shouldn't check, and instead attach an end event listener. When the stream ends you will get an end event.

If a [readable]stream is implemented correctly, you will get an end event when there is nothing left to read. For open-ended streams that don't end, you could implement an activity timer to see how long it's been since the stream was last readable, and decide after a certain amount of time to remove your listeners.

(function() {
    var timeout = null;
    var WAIT_TIME = 10 * 1000; // 10 Sec
    function stopListening( ) {
        stream.off('data', listener);
    }
    function listener( data ) {
        clearTimeout(timeout);
        timeout = setTimeout(stopListening, WAIT_TIME);
        // DO STUFF
    }
    timeout = setTimeout(stopListening, WAIT_TIME);
    stream.on('data', listener);
})();