Merkle Tree Implementation with Javascript and CryptoJS (SHA-256)

main.js

var MerkleTree  = require('./MerkleTree.js'),
    transaction = ['1', '2', '3', '4'],
    tree        = new MerkleTree(transaction);

tree.createTree();
console.log('>>> Log: ', tree.getOldTransaction());
console.log('>>> Root Hash: ', tree.getRootHash());

MerkleTree.js

/**
 * MerkleTree Implementation
 * @version 1.0.0
 * @author Ronny Amarante <[email protected]>
 */

var SHA256 = require("crypto-js/sha256");

function MerkleTree(transactions) {
  this.transactions    = transactions;
  this._oldTransaction = {};
}

MerkleTree.prototype = {

  getOldTransaction: function() { return this._oldTransaction; },

  getRootHash: function() {
    var idx = Object.keys(this._oldTransaction)[Object.keys(this._oldTransaction).length-1]
    return this._oldTransaction[idx]; 
  },

  createTree: function() {
    var transactions = this.transactions,
        temp         = [];

    for (var idx = 0; idx < this.transactions.length; idx += 2) { /** Iterate using 2 step's */
      var tr        = this.transactions[idx],
          hash      = { l: '', r: '' },
          pos_idx   = parseInt(idx)+1,
          pos_right;

      hash["l"] =  this._oldTransaction[tr] = String(SHA256(tr)); /** Apply SHA-256 hash to left pair transaction */
      
      (pos_idx != this.transactions.length) ? pos_right = this.transactions[pos_idx] : pos_right = ''; /** Declare value of right pair */

      if (pos_right != '') { /** Verify existence of right pair */
        hash["r"] = String(SHA256(pos_right)); /** Apply SHA-256 hash to right pair transaction */
        this._oldTransaction[this.transactions[pos_idx]] = hash["r"] ; /** Persist log */
        temp.push(hash["l"] + hash["r"]); /** Persist merge of both hash's */
      } else {
        temp.push(hash["l"]); /** Persist merge of left pair if donst have right pair */
      }
        
    }

    if (this.transactions.length != 1) {
      this.transactions = temp; /** Store changes of transactions */
      this.createTree(); /** Invoke recursive */
    }

  }

}

module.exports = MerkleTree;

MerkleTreeTest.js

var assert = require('chai').assert,
    MerkleTree = require('../lib/MerkleTree.js');

describe('MerkleTree', function() {
  
  describe('Even Number transaction for ["a", "b", "c", "d"]', function() {
    
    it('should return return the correct Root Hash', function(){
      var tree = new MerkleTree(['a', 'b', 'c', 'd']);
      tree.createTree();
      assert.equal(tree.getRootHash(),'58c89d709329eb37285837b042ab6ff72c7c8f74de0446b091b6a0131c102cfd');
    });

  });

  describe('Odd Number transaction for ["a", "b", "c", "d", "e"]', function() {
    
    it('should return return the correct Root Hash', function(){
      var tree = new MerkleTree(['a', 'b', 'c', 'd', 'e']);
      tree.createTree();
      assert.equal(tree.getRootHash(),'d6246621103b5050cf32df614c5017e91853d47a19fe5d3e7c68a8f4588f5b66');
    });

  });
  
});

output.md

 Log:  { 
  '1': '6b86b273ff34fce19d6b804eff5a3f5747ada4eaa22f1d49c01e52ddb7875b4b',
  '2': 'd4735e3a265e16eee03f59718b9b5d03019c07d8b6c51f90da3a666eec13ab35',
  '3': '4e07408562bedb8b60ce05c1decfe3ad16b72230967de01f640b7e4729b49fce',
  '4': '4b227777d4dd1fc61c6f884f48641d02b4d121d3fd328cb08b5531fcacdabf8a',
  '6b86b273ff34fce19d6b804eff5a3f5747ada4eaa22f1d49c01e52ddb7875b4bd4735e3a265e16eee03f59718b9b5d03019c07d8b6c51f90da3a666eec13ab35': '33b675636da5dcc86ec847b38c08fa49ff1cace9749931e0a5d4dfdbdedd808a',
  '4e07408562bedb8b60ce05c1decfe3ad16b72230967de01f640b7e4729b49fce4b227777d4dd1fc61c6f884f48641d02b4d121d3fd328cb08b5531fcacdabf8a': '13656c83d841ea7de6ebf3a89e0038fea9526bd7f686f06f7a692343a8a32dca',
  '33b675636da5dcc86ec847b38c08fa49ff1cace9749931e0a5d4dfdbdedd808a13656c83d841ea7de6ebf3a89e0038fea9526bd7f686f06f7a692343a8a32dca': '85df8945419d2b5038f7ac83ec1ec6b8267c40fdb3b1e56ff62f6676eb855e70' 
 }
 Root Hash:  '85df8945419d2b5038f7ac83ec1ec6b8267c40fdb3b1e56ff62f6676eb855e70'

package.json

{
  "name": "merkle-tree",
  "version": "1.0.0",
  "description": "Merkle Tree implementation",
  "scripts": {
    "start": "node lib/main.js",
    "test": "mocha test/MerkleTreeTest.js"
  },
  "author": "@amaranter",
  "license": "MIT",
  "devDependencies": {
    "chai": "^4.1.1",
    "crypto-js": "^3.1.9-1",
    "mocha": "^3.5.0"
  }
}