An example of building custom encoding/decoding functions to pack (well-defined and well-formed) data into smaller space.

custom-encoding.mjs

// Use the `Buffer` class. Requires Node.js.
import { Buffer } from "node:buffer";

/**
 * @typedef CommodityPrice
 * @property {string} id - A unique identifier for this piece of information
 * @property {string} commodityId - The identifier for the commodity
 * @property {Date} postedAt - When this price was posted
 * @property {number} price - The price of the commodity when posted
 */

/**
 * Validate commodity price information to ensure it conforms to the format required by the encoding function.
 *
 * @param {CommodityPrice} commodityPriceObject - A JavaScript object containing commodity price information
 *
 * @throws {Error} If `id` is not a valid UUID.
 * @throws {Error} If `commodityId` is not a valid UUID.
 * @throws {Error} If `postedAt` is not a valid `Date` object.
 * @throws {Error} If `price` is not a valid number.
 */
function validateCommodityPriceObject(commodityPriceObject) {
  if (!/^[0-9a-fA-F-]{36}$/.test(commodityPriceObject.id)) {
    throw new Error("Invalid UUID format for id");
  }

  if (!/^[0-9a-fA-F-]{36}$/.test(commodityPriceObject.commodityId)) {
    throw new Error("Invalid UUID format for commodityId");
  }

  if (!(commodityPriceObject.postedAt instanceof Date)) {
    throw new Error("postedAt must be a valid Date object");
  }

  if (isNaN(commodityPriceObject.price)) {
    throw new Error("Price must be a number");
  }
}

/**
 * Encode commodity price information from a JavaScript object into a custom buffer.
 *
 * @param {CommodityPrice} commodityPriceObject - A JavaScript object containing commodity price information
 * @returns {Buffer} A custom buffer containing commodity price information
 */
function encodeCommodityPrice(commodityPriceObject) {
  validateCommodityPriceObject(commodityPriceObject);

  const buffer = Buffer.alloc(48);

  buffer.write(commodityPriceObject.id.replace(/-/g, ""), 0, 16, "hex");
  buffer.write(
    commodityPriceObject.commodityId.replace(/-/g, ""),
    16,
    16,
    "hex"
  );
  buffer.writeDoubleLE(commodityPriceObject.postedAt.getTime(), 32);
  buffer.writeDoubleLE(commodityPriceObject.price, 40);

  return buffer;
}

/**
 * Decode commodity price information from a custom buffer to a JavaScript object.
 *
 * @param {Buffer} commodityPriceBuffer - A custom buffer containing commodity price information
 * @returns {CommodityPrice} A JavaScript object containing commodity price information
 */
function decodeCommodityPrice(commodityPriceBuffer) {
  if (commodityPriceBuffer.length !== 48) {
    throw new Error("Invalid buffer length");
  }

  const id = commodityPriceBuffer
    .toString("hex", 0, 16)
    .replace(/^(.{8})(.{4})(.{4})(.{4})(.{12})$/, "$1-$2-$3-$4-$5");
  const commodityId = commodityPriceBuffer
    .toString("hex", 16, 32)
    .replace(/^(.{8})(.{4})(.{4})(.{4})(.{12})$/, "$1-$2-$3-$4-$5");
  const postedAt = new Date(commodityPriceBuffer.readDoubleLE(32));
  const price = commodityPriceBuffer.readDoubleLE(40);

  return { id, commodityId, postedAt, price };
}

// EXAMPLE USAGE

// Create a JavaScript object containing commodity price information

/** @type {CommodityPrice} */
const commodityPriceObject = {
  id: "7acb9d5e-b83c-4537-893f-389ca70f67c1",
  commodityId: "5e5532f0-b6ca-49bc-a9e4-8354814a9be0",
  postedAt: new Date(),
  price: 1234,
};

console.log("Original object:", commodityPriceObject);
console.log(
  "Byte length:",
  Buffer.byteLength(JSON.stringify(commodityPriceObject), "utf8"),
  "\n\n"
);

// The object's size is 149 bytes

// Encode the object into a buffer

const commodityPriceBuffer = encodeCommodityPrice(commodityPriceObject);
console.log("Encoded buffer:", commodityPriceBuffer);
console.log("Byte length:", commodityPriceBuffer.byteLength, "\n");

// The buffer's size is 48 bytes. That's a 3.1:1 compression ratio. A 67.8% reduction in size.

// Decode the buffer back into an object

const decodedCommodityPrice = decodeCommodityPrice(commodityPriceBuffer);
console.log("Decoded object:", decodedCommodityPrice);
console.log(
  "Byte length:",
  Buffer.byteLength(JSON.stringify(decodedCommodityPrice), "utf8"),
  "\n\n"
);

// The object is back to 149 bytes