Merkle tree implementation

index.ts

/**
 * Converts a list of values into a list of pairs.
 * @param arr Single dimensional array of values.
 */
function toPairs(arr) {
  return Array.from(Array(Math.ceil(arr.length / 2)), (_, i) => arr.slice(i * 2, i * 2 + 2));
}

/**
 * Converts a list of values into a list of pairs.
 * @param arr Single dimensional array of values.
 */
function hashValue(value): string {
  return createHash('sha256').update(value).digest('hex');
}

/**
 * Converts a list of values into a list of pairs.
 * @param arr Single dimensional array of values.
 */
function hashList(arr): string[] {
  return arr.map((v) => hashValue(v));
}

/**
 * Hash pair values.
 * @param a Pair value.
 * @param b Pair value.
 */
function hashPair(a?, b?) {
  return b ? hashValue(`${a}${b}`) : a;
}

/**
 * Calculates merkle root hash.
 * @param arr Array of pairs.
 */
function toMerkle(arr) {
  return arr.length === 1 ? arr[0] : toMerkle(toPairs(arr).reduce((tree, pair) => [...tree, hashPair(...pair)], []));
}

/**
 * Run implementation.
 */
const values = ['foo', 'bar', 'baz'];
const root = toMerkle(hashList(values));
console.log(root);