Stream writable.writableObjectMode Property in Node.js

The writable.writableObjectMode property is used to check whether a writable stream is operating in object mode. It returns true if object mode is enabled, false if disabled, or undefined if not explicitly set.

Syntax

writable.writableObjectMode

Return Value

Returns a boolean value or undefined:

• true - Object mode is enabled
• false - Object mode is explicitly disabled
• undefined - Object mode not set (default)

Example 1: Stream with Object Mode Enabled

// Program to demonstrate writable.writableObjectMode property
// Importing the stream module
const stream = require('stream');

// Creating a data stream with writable and objectMode set to true
const writable = new stream.Writable({
    objectMode: true,
    // Writing the data from stream
    write: function(chunk, encoding, next) {
        // Converting the data chunk to be displayed
        console.log(chunk.toString());
        next();
    }
});

// Writing data
writable.write('Welcome to TutorialsPoint !');
writable.write('SIMPLY LEARNING');

// Checking if object mode is enabled
console.log('Object mode enabled:', writable.writableObjectMode);

Welcome to TutorialsPoint !
SIMPLY LEARNING
Object mode enabled: true

Example 2: Stream with Default Settings

// Program to demonstrate writable.writableObjectMode property
// Importing the stream module
const stream = require('stream');

// Creating a data stream with writable (default settings)
const writable = new stream.Writable({
    // Writing the data from stream
    write: function(chunk, encoding, next) {
        // Converting the data chunk to be displayed
        console.log(chunk.toString());
        next();
    }
});

// Writing data
writable.write('Welcome to TutorialsPoint !');
writable.write('SIMPLY LEARNING');

// Checking object mode status
console.log('Object mode status:', writable.writableObjectMode);
console.log('Type:', typeof writable.writableObjectMode);

Welcome to TutorialsPoint !
SIMPLY LEARNING
Object mode status: undefined
Type: undefined

Example 3: Stream with Object Mode Explicitly Disabled

// Creating a writable stream with objectMode explicitly set to false
const stream = require('stream');

const writable = new stream.Writable({
    objectMode: false,
    write: function(chunk, encoding, next) {
        console.log('Received:', chunk.toString());
        next();
    }
});

writable.write('Test data');
console.log('Object mode disabled:', writable.writableObjectMode);

Received: Test data
Object mode disabled: false

Key Points

• Object mode allows streams to work with JavaScript objects instead of just strings and Buffers
• The property is read-only and reflects the stream's configuration
• When undefined, the stream uses default buffer mode
• This property is useful for programmatically checking stream behavior

Conclusion

The writableObjectMode property helps determine if a writable stream operates in object mode. Use it to verify stream configuration and ensure compatibility with your data types.