Node.js zlib.deflate() Method

Last Updated : 11 Oct, 2021

The zlib.deflate() method is an inbuilt application programming interface of the Zlib module which is used to compress a chunk of data.

Syntax:

zlib.deflate( buffer, options, callback )

Parameters: This method accept three parameters as mentioned above and described below:

buffer: It can be of type Buffer, TypedArray, DataView, ArrayBuffer, and string.
options: It is an optional parameter that holds the zlib options.
callback: It holds the callback function.

Return Value: It returns the chunk of data after compression.

Below examples illustrate the use of zlib.deflate() method in Node.js:

Example 1:

// Node.js program to demonstrate the      
// deflate() method 
  
// Including zlib module 
const zlib = require("zlib"); 
  
// Declaring input and assigning 
// it a value string 
var input = "Geeks"; 
  
// Calling deflate method 
zlib.deflate(input, (err, buffer) => { 
  
  if (!err) { 
  
    console.log(buffer.toString('base64')); 
  }  
  else { 
    console.log(err); 
  } 
}); 
console.log("Data Compressed..."); 

Output:

Data Compressed...
eJxzT03NLgYABXQB8A==

Example 2:

// Node.js program to demonstrate the      
// deflate() method 
  
// Including zlib module 
const zlib = require("zlib"); 
  
// Declaring input and assigning 
// it a value string 
var input = "Geeks"; 
  
// Calling deflate method 
zlib.deflate(input, (err, buffer) => { 
  
  if (!err) { 
  
    console.log(buffer.toString('bas64')); 
  }  
  else { 
    console.log(err); 
  } 
}); 
console.log("Data Compressed..."); 

Output:

Data Compressed...
buffer.js:631
  throw new ERR_UNKNOWN_ENCODING(encoding);
  ^

TypeError [ERR_UNKNOWN_ENCODING]: Unknown encoding: bas64
    at stringSlice (buffer.js:631:9)    
    at Buffer.toString (buffer.js:667:10)    
    at Deflate.zlib.deflate [as cb] 
(/home/runner/BeautifulMiserlySourcecode/index.js:17:24)
    at Deflate.zlibBufferOnEnd (zlib.js:133:10)
    at Deflate.emit (events.js:203:15)
    at Deflate.EventEmitter.emit (domain.js:448:20)
    at endReadableNT (_stream_readable.js:1143:12)
    at process._tickCallback (internal/process/next_tick.js:63:19)

Here, an error occurs in encoding the data so, error is thrown.

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

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