HashDiff.rb

!/usr/bin/env ruby
# hash_delta.rb
# script to demonstrate hash diff algorithm
#

require 'json'

old_state = {
  n1: {
    position: { x: 1, y: 2},
  },
  n2: {
    position: { x: 3, y: 4},
  },
}

new_state = {
  n1: {
    position: { x: 1, y: 2},
  },
  n2: {
    position: { x: 3, y: 5},
  },
  n3: {
    position: { x: 6, y: 7},
  },
}

# javascript code for eql:
=begin

Object.prototype.eql = function (other) {
    var x = this
    var y = other
    // if both are function
    if (x instanceof Function) {
        if (y instanceof Function) {
            return x.toString() === y.toString();
        }
        return false;
    }
    if (x === null || x === undefined || y === null || y === undefined) { return x === y; }
    if (x === y || x.valueOf() === y.valueOf()) { return true; }

    // if one of them is date, they must had equal valueOf
    if (x instanceof Date) { return false; }
    if (y instanceof Date) { return false; }

    // if they are not function or strictly equal, they both need to be Objects
    if (!(x instanceof Object)) { return false; }
    if (!(y instanceof Object)) { return false; }

    var p = Object.keys(x);
    return Object.keys(y).every(function (i) { return p.indexOf(i) !== -1; }) ?
            p.every(function (i) { return objectEquals(x[i], y[i]); }) : false;
}
=end

def find_difference(old_state,new_state)
  diff = {}
  new_state.keys.each do |key|
    new_obj = new_state[key]
    old_obj = old_state[key]
    new_obj.keys.each do |property|
      unless old_obj && old_obj[property].eql?(new_obj[property])
        diff[key] ||= {}
        diff[key][property] = new_obj[property].clone
      end
    end
  end
  return diff
end


d = find_difference(old_state,new_state)

puts d.to_json