Data binding implementation in es6

keypath.es6

export class KeyPath {
  static lastValue(keypath, object) {
    return keypath.split('.').reduce((prev, curr) => {
      return prev && prev[curr];
    }, data);
  }
  
  static lastKey(keypath, object) {
    return keypath.split('.').pop();
  }
  
  static keyUp(keypath) {
    keypath = keypath.split('.');
    keypath.pop();
    return keypath.join('.')
  }
  
  static keyDown(keypath, next) {
    keypath = keypath.split('.');
    keypath.push(next);
    return keypath.join('.');
  }
  
  static lastObject(keypath, object) {
    return KeyPath.lastValue(KeyPath.keyUp(), object);
  }
}

observable.es6

import {KeyPath} from './keypath.es';

export class Observable {
  static simpleProperty(object, prop, watcher) {
    var config = {enumerable: true};
    
    Object.defineProperty(object, `__${prop}__`, {
      enumerable: false,
      value: object[prop]
    });
    
    config.get = () => {
      return object[`__${prop}__`];
    }
    
    config.set = (newVal) => {
      watcher(newVal, object[prop]);
      object[`__${prop}__`] = newVal;
    };
    
    Object.defineProperty(object, prop, config);
  }
  
  static array(array, watcher) {
    // hide defualt implementations
    ['push', 'pop', 'shift', 'unshift'].forEach((prop) =>{
      Object.defineProperty(array, `__${prop}__`, {
        enumerable: false,
        value: array[prop]
      });
    });

    Object.defineProperties(array, {
      assign: {
        enumerable: false,
        writable: false,
        value: (index, val) => {
          var oldArray = new Array(...array);
          var oldItem = array[index];
          watcher(array, oldArray, val, oldItem, index);
        }
      },
      push: {
        enumerable: false,
        writable: false,
        value: (...args) => {
          args.forEach(function (item) {
            var oldArray = new Array(...array);
            array.__push__(item);
            watcher(array, oldArray, item);
          });
          return array.length;
        }
      },
      pop: {
        enumerable: false,
        writable: false,
        value: () => {
          var oldArray = new Array(...array);
          var item = array.__pop__();
          watcher(array, oldArray, item);
        }
      },
      shift: {
        enumerable: false,
        writable: false,
        value: () => {
          var oldArray = new Array(...array);
          var item = array.__shift__();
          watcher(array, oldArray, item);
        }
      },
      unshift: {
        enumerable: false,
        writable: false,
        value: (...args) => {
          args.forEach(function (item) {
            var oldArray = new Array(...array);
            array.__unshift__(item);
            watcher(array, oldArray, item);
          });
          return array.length;
        }
      }
    });
  }
}