Node.js

Compress a File to Gzip with Custom Metadata

See more Gzip Examples

This example demonstrates how to use the CompressFile method to create a Gzip (.gz) file while customizing the metadata embedded in the Gzip header.

Before compression, several properties are set:

• Comment: Adds a descriptive comment to the Gzip file.
• Filename: Specifies the filename to embed in the Gzip data, which may be used by extraction tools as the default output name.
• CompressionLevel: Controls the tradeoff between compression ratio and speed (set to maximum in this example).
• LastModStr: Sets the last-modified timestamp using an RFC 822 formatted date string.

After setting these properties, the input file is compressed and written to a .gz file. This approach allows you to embed meaningful metadata along with the compressed data.

Node.js

NODEJS_PRELUDE

function chilkatExample() {

    var success = false;

    //  This example demonstrates how to compress a file to Gzip format
    //  while setting custom metadata such as comment, filename,
    //  compression level, and last-modified date.

    var gzip = new chilkat.Gzip();

    //  Set custom Gzip properties:
    gzip.Comment = "Example Gzip file created with Chilkat";
    gzip.Filename = "custom_name.txt";
    gzip.CompressionLevel = 9;
    gzip.LastModStr = "Wed, 1 Apr 2025 12:45:26 -0500";

    //  The file to be compressed:
    var inputFile = "example.txt";
    var outputFile = "example.txt.gz";

    //  Compress the file:
    success = gzip.CompressFile(inputFile,outputFile);
    if (success == false) {
        console.log(gzip.LastErrorText);
        return;
    }

    console.log("Compression successful.");
    console.log("Gzip file created: " + outputFile);

}

chilkatExample();