How to use 'zlib.unzip()' function in Node.js

In this shot, we learn how to decompress a string or a buffer using the zlib module in Node.js.

The zlib.unzip() function is a built-in module in Node.js that accepts, at most, three distinct parameters.

Syntax

The zlib.unzip() function looks like this when implemented in a program:

zlib.unzip(buffer, options, callback)

  • buffer: We use buffers to represent a fixed-length sequence of bytes. In the unzip() module, we can include buffers of <TypedArray>, <DataView>, <ArrayBuffer>, and <string> type.

  • options: These are optional objects that we can include in unzip() as a parameter.

  • callback: This is a function that is executed upon the method returning.

zlib.unzip() module

Code

Let’s look at the following implementation of the zlib.unzip() module in Node.js.

var zlib = require("zlib");
var text1 = "Hello this is a string";
zlib.gzip(text1, (err, buffer) => {
	zlib.unzip(buffer, (err, buffer) => {
		console.log("Decompressed string in base64 format:");
		console.log(buffer.toString('base64'));
	});
});
var text2 = "Hello this is another string";
zlib.gzip(text2, (err, buffer) => {
	zlib.unzip(buffer, (err, buffer) => {
		console.log("\nDecompressed string in utf8 format:");
		console.log(buffer.toString('utf8'));
	});
});

Explanation

The above code example imports the necessary library zlib required to execute the following code appropriately.

The zlib.unzip() takes three parameters, as mentioned previously. This function takes a text, an err (error parameter), and a buffer.

text1 is decompressed into base64 to print an unreadable message, as shown on the console. text2 is displayed in utf-8 format.

Note: The == sequence in the output generated for text1 indicates padding of one byte when a 24-bit section is not complete. If it contained =, it would mean a padding of two bytes.

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