Node.js Stream writable.writableFinished Property
With the open-source, cross-platform Node.js runtime environment, programmers may use JavaScript to create networking and server-side applications. The stream module is one of the main components of Node.js. It is made to effectively manage streaming data. Streams can handle data in pieces. Therefore, they are ideal for managing huge files or data that arrive gradually. For instance, data arriving via a network. Thus, they are integral features of Node.js.
Many classes are available in the stream module. These include Readable, Writable, Duplex, and Transform. All these classes are designed to handle various kinds of streaming data operations.
Writable Streams
Node.js's writable streams offer an abstraction for locations, like files, network sockets, or other writable endpoints, where data may be written over time. They are necessary for effectively and asynchronously managing massive volumes of data. The _write() function, which manages the actual data writing logic, is commonly implemented by inheriting it from the Writable class to create a writable stream.
Example:
Let us take a simple example to implement the Node.js riWtable Streams() Property.
const { Writable } = require('stream');
class wr extends Writable {
_write(chunk, encoding, callback) {
console.log(chunk.toString());
callback();
}
}
const w = new wr();
w.write('Hello, how are you?');
Output:
Explanation:
In this example, the MyWritable class implements the _write function and derives from Writable. The _ write method is invoked every time data is to be written to the stream.
What is the writable.writableFinished Property?
The writable property is a boolean function of writable streams. The writableFinished() function shows whether or not the stream has completed writing data. Understanding the lifespan of the writable stream is essential, as it is a component of its internal state management.
Syntax:
It has the following syntax:
writable.writableFinished
Key Characteristics of writable.writableFinished() Property:
There are several key characteristics of writable.writeableFinished() property. Some main characteristics are as follows:
- Read-only Property: It is not possible to directly set this read-only Property. The writable stream implementation is responsible for internal management of it.
- It is a measure of the lifecycle when the stream has completed writing all of the data, the writable.writableFinished property changes to true. It usually occurs following the call to the end function and the flushing of all buffered data.
- State Coordination: The Property is especially helpful in situations when we need to ascertain if a stream has finished writing operations. It allows us to check without listening to events. It is because it is synchronized with the internal state of the stream.
- Application: Applications frequently utilize the writable, especially those that need to know when a stream of data has completed processing. Writable Property came to an end. It is common when handling several streams and complex stream pipelines.
- Stream Lifecycle and Error Handling: Managing errors is a crucial aspect of working with streams. If something goes wrong while writing, the stream will release an error event. Appropriate error handling guarantees the correct closure of the stream. The release of resources will also occur.
Example:
Here's an example:
const { Writable } = require('stream');
const wr = new Writable({
write(chunk, encoding, callback) {
if (chunk.toString() === 'error') {
callback(new Error('Something went wrong!'));
} else {
process.stdout.write(chunk.toString());
callback();
}
}
});
wr.on('error', (err) => {
console.error('Stream error:', err);
});
wr.write('Hello, world!
');
wr.write('error');
wr.end('Goodbye, world!
');
wr.on('finish', () => {
console.log('Stream finished:', wr.writableFinished);
});
Output:
Explanation:
If an error occurs in this instance when writing, it is handled, and the error event is triggered so that the application is aware of the error and may react accordingly. Notably, the procedure will fail in the event of a mistake. Due to this, the writable.finished property will not be true if the stream is unable to finish properly.
Practical Uses
The Writable.WritableFinished property has many practical uses in the real world, especially in situations like these:
- Writing a file: Make sure that a file is written all the way through before moving on to the next step.
- Network Communication: Before ending a network connection or taking any further action, make sure that all data has been delivered across it.
- Data Processing Pipelines: Controlling the status of completion of intricate data processing pipelines that connect several streams.
For example, consider an application that handles and uploads big files to a cloud storage provider. Using the writable.writableFinished property, the application can ensure that the entire file has been uploaded before confirming the operation’s success or moving on to the next file.