Pretty fast base85 JavaScript library.

Aimed to encoding binary data (Uint8Array).

encode encodes the input Uint8Array into base85 String.

decode decodes the input base85 String into Uint8Array.

charset is "z85" by default.

Binary data encoding example:

// png image, 169 bytes
const imageBytes = new Uint8Array([137,80,78,71,13,10,26,10,0,0,0,13,73,72,68,82,0,0,0,32,0,0,0,32,8,2,0,0,0,252,24,237,163,0,0,0,1,115,82,71,66,0,174,206,28,233,0,0,0,4,103,65,77,65,0,0,177,143,11,252,97,5,0,0,0,9,112,72,89,115,0,0,14,195,0,0,14,195,1,199,111,168,100,0,0,0,62,73,68,65,84,72,75,237,210,49,10,0,48,8,197,80,239,127,105,187,252,161,208,150,32,93,243,86,149,44,86,191,213,33,131,9,3,200,0,50,128,12,160,92,74,63,242,77,55,217,216,100,48,97,0,25,64,6,144,1,208,189,0,183,189,228,126,66,93,37,1,0,0,0,0,73,69,78,68,174,66,96,130]);
const base85 = encode(imageBytes);

console.log(base85);
console.log(base85.length);
// "Ibl@q4gj0X0000dnK#lE0000w0000w2M:#a0q)Y3Qw$n]0DRdeliagl9o^C600D}2o*F:VV5Yp<vfDSh010Qns-TMy4-nnD4-ns/z(vgD002hOl{T^yoypdZ3ih:=-zD2Mx$Kqp^3t!W]h.bcr>)fdG9.U305x6kPJ>8N[>z6@/KMWA02X3aKo9.w0jPV5ENmr^0rr9107/QOm6n<:F="
// 212

If you need to encode a text (are you really need it?) use TextEncoder/TextDecoder.

const input = "Man is distinguished";
const inputBytes = utf8StringToArrayBuffer(input);
console.log(encode(inputBytes, "ascii85"));  // "9jqo^BlbD-BleB1DJ+*+F(f,q"
console.log(encode(inputBytes, "z85"));      // "o<}]Zx(+zcx(!xgzFa9aB7/b}"

const outputBytes = decode("9jqo^BlbD-BleB1DJ+*+F(f,q", "ascii85");
const output = arrayBufferToUtf8String(outputBytes);
console.log(output); // "Man is distinguished"

For more examples see the tests.

You can test the lib online in the browser's console: https://alttiri.github.io/base85/online

All required things are already in the global scope. (encode, decode; util functions: utf8StringToArrayBuffer and others; Tester class too.)

Note. The optimisation for "ascii85" by replacing "\0\0\0\0" by "z" instead of "!!!!!" and " " (4 spaces) by "y" instead of "+<VdL" is not supported.

Anyway nobody forbids you to do something like base85.replaceAll("!!!!!", "z") as well as to add "<~", "~>" manually if you need it.

To install you need fisrt to create .npmrc file with @alttiri:registry=https://npm.pkg.github.com content:

echo @alttiri:registry=https://npm.pkg.github.com >> .npmrc

only then run

npm install @alttiri/base85

Note, that GitHub Packages requires to have also ~/.npmrc file by //npm.pkg.github.com/:_authToken=TOKEN content, where TOKEN is a token with the read:packages permission, take it here https://github.com/settings/tokens/new.

Or install the lastest version from GitHub directly:

npm install git+https://github.com/alttiri/base85.git

No need extra actions. Also you can specify a semver with appending, for example, #semver:1.2.0 to git-URL.

The same by adding this line in package.json's dependencies field:

"@alttiri/base85": "github:alttiri/base85#semver:1.2.0"

Or just copy-paste the file from the repo. It's standalone.