Convert between zero-decimal (integer) and decimal number for currency (for Stripe / Shopify / etc)

rebaseCurrency.js

/**
 * https://shopify.dev/docs/api/ajax/reference/product
 * https://stripe.com/docs/currencies#zero-decimal
 */
function rebaseCurrency(
  /** @type {number} */ price,
  /** @type {string} */ isoCurrency,
  /** @type {"toZeroDecimal" | "fromZeroDecimal"} */ transform
) {
  const zeroDecimalCurrencies = [
    "BIF",
    "CLP",
    "DJF",
    "GNF",
    "JPY",
    "KMF",
    "KRW",
    "MGA",
    "PYG",
    "RWF",
    "UGX",
    "VND",
    "VUV",
    "XAF",
    "XOF",
    "XPF",
    // special cases; following assumed 0 decimals?
    "ISK",
    "HUF",
    "TWD",
    "UGX",
  ];

  const threeDecimalCurrencies = ["BHD", "JOD", "KWD", "OMR", "TND"];
  let base = 100;
  if (zeroDecimalCurrencies.includes(isoCurrency)) base = 1;
  if (threeDecimalCurrencies.includes(isoCurrency)) base = 1000;
  return transform === "toZeroDecimal" ? price * base : price / base;
}