Gzip a string in javascript using pako.js

Question

I was able to decompress a string in JavaScript using pako.js

// Get some base64 encoded binary data from the server. Imagine we got this:
var b64Data     = 'H4sIAAAAAAAAAwXB2w0AEBAEwFbWl2Y0IW4jQmziPNo3k6TuGK0Tj/ESVRs6yzkuHRnGIqPB92qzhg8yp62UMAAAAA==';

// Decode base64 (convert ascii to binary)
var strData     = atob(b64Data);

// Convert binary string to character-number array
var charData    = strData.split('').map(function(x){return x.charCodeAt(0);});

// Turn number array into byte-array
var binData     = new Uint8Array(charData);

// Pako magic
var data        = pako.inflate(binData);

// Convert gunzipped byteArray back to ascii string:
var strData     = String.fromCharCode.apply(null, new Uint16Array(data));

// Output to console
console.log(strData);

I want a method to compress string and output can be decompressed by above code using pako and gzip.

How can I do that?

What's going wrong when you simply do what's written in the docs? Note that pako has options to compress/decompress to/from string, so your typed array is not necessary. — ASDFGerte
– ASDFGerte, Commented Jun 4, 2018 at 13:20
@ASDFGerte I am doing var str ="Hello world"; var test = pako.gzip(new Uint8Array(str), {to: 'string'}); alert(btoa(test)); I get same output " H4sIAAAAAAAAAwMAAAAAAAAAAAA= " for any string and also not able to get back the original string after decompressing the output. Where am I going wrong? — sireesha
– sireesha, Commented Jun 5, 2018 at 5:32
The way you construct your Uint8Array is not working (always empty) - debugging your test for a short moment would quickly tell you that. You could fix that, but way easier is noticing that in gzip(data[, options]), data has a described type of "Uint8Array | Array | String", which means you can just do let test = pako.gzip(str, {to: 'string'});. Reverting the process is as simple as pako.ungzip(test, { to: 'string' });. — ASDFGerte
– ASDFGerte, Commented Jun 5, 2018 at 8:06

Vijay Chavda · Accepted Answer · 2021-02-04 12:35:38Z

6

Compression:

let compressed_str = pako.gzip(str, {to: 'string'});

Decompression:

let original_str = pako.ungzip(compressed_str, { to: 'string' });

edited Feb 4, 2021 at 12:35

Vijay Chavda

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answered Jun 6, 2018 at 5:50

sireesha

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2 Comments

recolic Over a year ago

The compressed string looks like this: 31,139,8,0,0,0,0,0,0,3,203,72,205,201,201,87,200,64,144,0,128,136,249,229,17,0,0,0, but I think the question is asking for base64 encoded string

Hawkeye Parker Over a year ago

pako no longer accepts {to: 'string'}. It returns a uIntArray, which needs to be converted to a string. If sending over HTTP, the most simple/common method I've seen is window.btoa(String.fromCharCode.apply(null, pakoGzippedData)). There are many other ways

recolic · Accepted Answer · 2023-04-05 00:20:55Z

2

There is a duplicate question, so I'm sharing my answer here.

https://stackoverflow.com/a/75934779/7295761

{to: 'string'} simply doesn't work for latest pako.js

answered Apr 5, 2023 at 0:20

recolic

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