(Node.js) Compressing StringBuilder Data Using CompressSb (Single Call and Chunked)

See more Compression Examples

1. Single-call compression, where the entire input is compressed in one operation.
2. Chunked compression, where the input is split into multiple parts and processed sequentially using the FirstChunk and LastChunk properties.

The example shows how compressed output is appended to a BinData object, and how the result can be verified by decompressing back to the original text. This is useful for both simple use cases and scenarios where data is processed incrementally (such as streaming or large inputs).

Key Points

• CompressSb converts text to bytes using the Charset property (UTF-8 recommended).
• Compressed data is appended to a BinData object.
• When both FirstChunk and LastChunk are true, compression is done in a single call.
• For chunked processing:
  • First chunk → FirstChunk = true, LastChunk = false
  • Middle chunks → both false
  • Final chunk → LastChunk = true
• Chunked compression is useful when processing data incrementally.

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOS

var os = require('os');
if (os.platform() == 'win32') {  
  var chilkat = require('@chilkat/ck-node23-win64'); 
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node23-linux-arm');
    } else if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node23-linux-arm64');
    } else {
        var chilkat = require('@chilkat/ck-node23-linux-x64');
    }
} else if (os.platform() == 'darwin') {
  var chilkat = require('@chilkat/ck-node23-mac-universal');
}

function chilkatExample() {

    var success = false;

    // This example assumes the Chilkat API has already been unlocked.
    // See Global Unlock Sample for sample code.

    var compress = new chilkat.Compression();
    compress.Algorithm = "zlib";

    // ================================================================
    // 1) Single-call compression (entire data in one call)
    // ================================================================

    var sb = new chilkat.StringBuilder();
    sb.Append("The quick brown fox jumps over the lazy dog. ");
    sb.Append("This is a simple example using CompressSb.");

    var bdCompressed = new chilkat.BinData();

    // When both FirstChunk and LastChunk are true (the defaults),
    // the entire compression happens in a single call.
    compress.FirstChunk = true;
    compress.LastChunk = true;

    success = compress.CompressSb(sb,bdCompressed);
    if (success == false) {
        console.log(compress.LastErrorText);
        return;
    }

    var compressedBase64 = bdCompressed.GetEncoded("base64");

    console.log("Single-call compressed (base64):");
    console.log(compressedBase64);

    // ================================================================
    // 2) Chunked compression using FirstChunk / LastChunk
    // ================================================================

    var bdChunkedOut = new chilkat.BinData();

    // First chunk
    compress.FirstChunk = true;
    compress.LastChunk = false;

    var sbPart = new chilkat.StringBuilder();
    sbPart.Append("The quick brown fox ");

    success = compress.CompressSb(sbPart,bdChunkedOut);
    if (success == false) {
        console.log(compress.LastErrorText);
        return;
    }

    // Middle chunk
    compress.FirstChunk = false;
    compress.LastChunk = false;

    sbPart.Clear();
    sbPart.Append("jumps over the lazy dog. ");

    success = compress.CompressSb(sbPart,bdChunkedOut);
    if (success == false) {
        console.log(compress.LastErrorText);
        return;
    }

    // Final chunk
    compress.FirstChunk = false;
    compress.LastChunk = true;

    sbPart.Clear();
    sbPart.Append("This is a chunked CompressSb example.");

    success = compress.CompressSb(sbPart,bdChunkedOut);
    if (success == false) {
        console.log(compress.LastErrorText);
        return;
    }

    var chunkedBase64 = bdChunkedOut.GetEncoded("base64");

    console.log("Chunked compressed (base64):");
    console.log(chunkedBase64);

    // ================================================================
    // 3) Decompress to verify correctness
    // ================================================================

    var sbDecompressed = new chilkat.StringBuilder();

    // Decompress in a single call (entire data already assembled)
    compress.FirstChunk = true;
    compress.LastChunk = true;

    success = compress.DecompressSb(bdChunkedOut,sbDecompressed);
    if (success == false) {
        console.log(compress.LastErrorText);
        return;
    }

    console.log("Decompressed text:");
    console.log(sbDecompressed.GetAsString());

}

chilkatExample();