Encode and decode MessagePack

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MessagePack is a binary serialization format with the same data model as JSON. The binary encoding is smaller and faster to parse, which makes it a good fit for caches, message queues and service to service traffic. The Standard Library implements it in jsr:@std/msgpack.

import { decode, encode } from "jsr:@std/msgpack";

We encode a value that could just as well be JSON.

const value = {
  name: "Deno",
  version: 2,
  tags: ["fast", "secure"],
  active: true,
  score: 99.5,
};

To encode, pass the value to the encode function. The result is a Uint8Array, noticeably smaller than the JSON text of the same value.

const bytes = encode(value);
console.log(bytes.length); // 61
console.log(JSON.stringify(value).length); // 79

To decode, pass the bytes to the decode function. The round trip returns an equivalent value.

const decoded = decode(bytes);
console.log(decoded);
// {
//   name: "Deno",
//   version: 2,
//   tags: [ "fast", "secure" ],
//   active: true,
//   score: 99.5
// }

MessagePack supports two types that JSON lacks: raw binary data and bigint. Both survive the round trip without any base64 tricks.

const binary = decode(encode({ data: new Uint8Array([1, 2, 3]), big: 123n }));
console.log(binary); // { data: Uint8Array(3) [ 1, 2, 3 ], big: 123n }

The full set of supported value types is null, boolean, number, bigint, string, Uint8Array, and arrays and plain objects of those. Anything else, for example a Date or a Map, makes encode throw an error.

Run this example locally using the Deno CLI:

deno run https://docs.deno.com/examples/scripts/msgpack_encoding.ts

Encode and decode MessagePack

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