Writable Streams: Writing a Stream and Backpressure
Learn how to write to a stream and the backpressure mechanism.
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A Writable stream represents a data destination. Imagine, for instance, a file on the filesystem, a database table, a socket, the standard error, or the standard output interface. In Node.js, it’s implemented using the Writable abstract class, which is available in the stream module.
Writing to a stream
Pushing some data down a Writable stream is a straightforward business; all we have to do is use the write() method, which has the following signature:
writable.write(chunk, [encoding], [callback])
The encoding argument is optional and can be specified if chunk is a string (it defaults to utf8, and it’s ignored if chunk is a buffer). The callback function, on the other hand, is called when the chunk is flushed into the underlying resource and is optional as well.
To signal that no more data will be written to the stream, we have to use the end() method:
writable.end([chunk], [encoding], [callback])
We can provide a final chunk of data through the end() method; in this case, the callback function is equivalent to registering a listener to the finish ...