ZLIB

The Node.js Zlib module is used to provide compression and decompression (zip and unzip) functionalities. It is implemented using Gzip and deflate/inflate.

The zlib module can be accessed using:

snippet

const zlib = require('zlib');

Compressing and decompressing a file can be done by piping the source stream data into a destination stream through zlib stream.

Node.js ZLIB Example: Compress File

Let's see a simple example of Node.js ZLIB module to compress a file "input.txt" into "input.txt.gz".

File: zlib_example1.js

snippet

const zlib = require('zlib');
const gzip = zlib.createGzip();
const fs = require('fs');
const inp = fs.createReadStream('input.txt');
const out = fs.createWriteStream('input.txt.gz');
inp.pipe(gzip).pipe(out);

We have a text file named "input.txt" on the desktop.

Open Node.js command prompt and run the following code:

snippet

node zlib_example1.js

You can see that it will produce a compressed file named "input.txt.gz" on the desktop.

Node.js ZLIB Example: Decompress File

Let's see a simple example of Node.js ZLIB module to decompress a file "input.txt.gz" into "input2.txt".

File: zlib_example2.js

snippet

const zlib = require('zlib');  
const unzip = zlib.createUnzip();
const fs = require('fs');
const inp = fs.createReadStream('input.txt.gz');
const out = fs.createWriteStream('input2.txt');

inp.pipe(unzip).pipe(out);

snippet

node zlib_example2.js

Now you will see that same code of "input.txt" is available into "input2.txt" file.

Note

To understand this example well, create "input.txt" file having a large amount of data. Let's assume it has 40 kb data. After compressing this file you will get the size of compressed file "input.txt.gz" to 1 kb only. After decompressing the "input.txt.gz" file, you will get 40 kb of same data into "input2.txt" file.