Node.js zlib.bytesWritten Property

The zlib.bytesWritten property is an application programming interface of the zlib module which is used to specify the number of bytes written to the engine before the bytes are processed (compressed or decompressed, as proper for the derived class).

Syntax:

zlib.bytesWritten

Return Value: It returns the number of bytes written to the engine. 

The below examples illustrate the use of zlib.bytesWritten method in Node.js:

Example 1:

javascript

// Node.js program to demonstrate the
// zlib.bytesWritten Property

// Including assert and zlib
// module
const zlib = require('zlib');
const assert = require('assert');

// Input to be written
const input = Buffer.from('0123456789012345678901');

// Calling deflate method
zlib.deflate(input, (err, deflatedBuffer) => {
    assert(!err);

    // Declaring buffer and numberRead
    let numberRead = 0;
    let buffers = [];

    // Creating a zip object
    const stream = zlib.createGzip()

        // Data event
        .on('data', function (chunk) {
            buffers.push(chunk);
            numberRead += chunk.length;
        })

        // end event
        .on('end', function () {

            // Calling bytesWritten property
            console.log(stream.bytesWritten);

        })
        .end(deflatedBuffer);
});

Output:

21

Example 2:

javascript

// Node.js program to demonstrate the
// zlib.bytesWritten property

// Including zlib module
const zlib = require('zlib');

// Input to be written
const input = Buffer.from('NidhiSingh1352');

// Calling deflateRaw method
zlib.deflateRaw(input, (err, buffer) => {

    // Creating a Deflate object
    const zlibs = zlib.Deflate()

        // Data event
        .on('data', function (chunk) { })

        // end event
        .on('end', function () {

            // Calling bytesWritten property
            console.log(zlibs.bytesWritten);

        })
        .end(buffer);
});

Output:

16

Reference: https://nodejs.org/api/zlib.html#zlib_zlib_byteswritten