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What is ZLIB in Node.js?
- zlib is a software library used for data compression.
- 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
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.

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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".
- Node JS Tutorial File: zlib_example1.js
zlib_example1.js
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.

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- Open Node.js command prompt and run the following code:
- node zlib_example1.js

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

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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".
- Node JS Tutorial File: zlib_example2.js
zlib_example2.js
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);
- Now you will see that same code of "input.txt" is available into "input2.txt" file.