The **`zlib` module** in Node.js provides compression and decompression functionality utilizing Gzip, Deflate/Inflate, and Brotli.

It can be accessed in your program with: 

```js
const zlib = require('zlib');
```

**`deflateRaw()`** is a function of the `zlib` module, which allows compressing a stream of data.

# Syntax

```JS
zlib.deflateRaw( buffer, options, callback )
```
# Parameters

* **`buffer`** is the data to be decompressed. It can be of any type, such as  Buffer, TypedArray, DataView, ArrayBuffer, or string. 

* **`options`** is an optional argument used to provide options to the `zlib` classes.
* **`callback`** is the call-back function that is executed.

# Return value

The `deflateRaw()` method returns compressed data.

# Example

In the following example, we provide an input string to the `deflateRaw()` method, which compresses the input in line 8. 

// Including zlib module
const zlib = require("zlib");
  
//input declaration
var input = "Educative Inc.";
  
// Calling zlib.deflateRaw to compress data
zlib.deflateRaw(input, (err, buffer) => {
  console.log("Compressed data: ",buffer.toString('utf8'));
  });

What is deflateRaw() in Node.js?

Compresses data using deflate algorithm; returns compressed data as a buffer or string.