Node.js stream.finished() Method

The stream.finished() method is utilized to receive an alert if a stream is not writable or readable anymore or if it had experienced an error or a close event that is immature.

Syntax:  

stream.finished(stream, options, callback)

Parameters: This method accepts three parameters as mentioned above and described below:  

• stream: This parameter can be readable or writable.
• options: This is an object, which can be: 
  
  • It can be an error i.e. if it is set to false, then a call to emit events('error', err) is not considered as finished and by default it is true.
  • It can be readable i.e. if it is set to false, then a callback function is called when the stream ends still the stream can be readable and by default it is true.
  • It can be writable i.e. When set to false, then a callback function is called when the stream ends still the stream can be writable and by default it is true.
• callback: A callback function that takes an elective error argument.

Return Value: It returns a cleanup function that detaches all the registered listeners.

The below examples illustrate the use of the stream.finished() method in Node.js:

Example 1:  

Output: 

Promise { <pending> }
Readable is being consumed

Example 2:  

Output: Here, an error occurs while writing the file name so an error is returned in the output.

Promise { <pending> }
{ [Error: ENOENT: no such file or directory, open 'input.text'] 
errno: -2, code: 'ENOENT', syscall: 'open', path: 'input.text' }

Reference: https://nodejs.org/api/stream.html#stream_stream_finished_stream_options_callback