const HashBase = require('hash-base');
const inherits = require('inherits');

// our hash function is XOR sum of all bytes
function MyHash () {
	HashBase.call(this, 1); // in bytes

	this._sum = 0x00;
};

inherits(MyHash, HashBase)

MyHash.prototype._update = function () {
	for (let i = 0; i < this._block.length; ++i) {
		this._sum ^= this._block[i];
	}
};

MyHash.prototype._digest = function () {
	return this._sum;
};

const data = Buffer.from([0x00, 0x42, 0x01]);
const hash = new MyHash().update(data).digest();
console.log(hash); // => 67