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How to use 'zlib constants' in Node.js

Dian Us Suqlain

Zlib is a built-in module in Node.js that provides decompression or compression properties on strings and buffers in a program.

The zlib.constants include dozens of operations that we do not need to include separately in our program. Those operations include:

  • Flush values
  • Return codes for compression and decompression functions
  • The deflate compression method
  • Initializing zalloc, zfree, and opaque
  • Compression strategy
  • Compression levels

These constant operations are pre-loaded every time we include the zlib.constant in our program.

Some Zlib.constant built-in operations

Syntax

As stated above, we do not need to define the constants by ourselves. The basic syntax of constant operations is as follows:

#define Z_NO_FLUSH 
#define Z_STREAM_END
#define Z_NO_COMPRESSION
#define Z_BINARY

Code

For better understanding, observe the following code illustration.

const zlib = require("zlib");

console.log("Values for constants:")
console.log("Z_NO_FLUSH: ", zlib.constants.Z_NO_FLUSH)
console.log("Z_STREAM_END: ", zlib.constants.Z_STREAM_END)
console.log("Z_MEM_ERROR: ", zlib.constants.Z_MEM_ERROR)
console.log("Z_BUF_ERROR: ", zlib.constants.Z_BUF_ERROR)
console.log("Z_NO_COMPRESSION: ", zlib.constants.Z_NO_COMPRESSION)
console.log("Z_DEFAULT_STRATEGY: ", zlib.constants.Z_DEFAULT_STRATEGY)
Zlib.constant operation values

Explanation

The above code prints the levels for constants used in the example. zlib module is imported in the program by typing const zlib = require("zlib");.

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