blog-historical-object

blog-historical-object.js

//context: http://www.nicholascloud.com/2012/04/historical-javascript-objects/

var historicalObject = (function () {

  var _pushProto = function (obj) {
    function EmptyObject () {}
    EmptyObject.prototype = obj || Object.prototype;
    var other = new EmptyObject();
    if (other.__version !== undefined) {
      other.__version++;
    } else {
      other.__version = 1;
    }
    return other;
  };

  var _popProto = function (obj) {
    var proto = Object.getPrototypeOf(obj);
    if (proto === Object.prototype) {
      return obj;
    }
    return proto;
  };

  return {
    create: function (base) {
      var obj = _pushProto(base);
      obj.revise = function () {
        return _pushProto(this);
      };
      obj.revert = function (howFar) {
        if (typeof howFar !== 'number') {
          howFar = 1;
        }
        var other = _popProto(this);
        howFar--;
        if (howFar === 0) {
          return other;
        }
        return other.revert(howFar);
      };
      return obj;
    }
  };
})();

var person = function (name, permissions) {

  return historicalObject.create({
    setName: function (name) {
      var other = this.revise();
      other.getName = function () {
        return name;
      };
      return other;
    },
    getName: function () {
      return name;
    },
    elevate: function () {
      if (!permissions.indexOf('admin') < 0) {
        return;
      }
      var _this = this;
      var other = this.revise();
      other.isAdmin = true;
      other.toString = function () {
        return "(admin) " + _this.toString();
      };
      return other;
    },
    toString: function toString () {
      var str = "[" + this.__version + "]::" + this.getName();
      var proto = Object.getPrototypeOf(this);
      if (proto.hasOwnProperty('__version')) {
        str += ' -> ' + proto.toString();
      }
      return str;
    }
  });
};

var p = person('Walter', ['admin'])
  .setName('Walter Williams')
  .setName('Walter T. Williams')
  .setName('Walt');

console.log(p.toString());
p = p.revert();
console.log(p.toString());

p = p.elevate();
console.log(p.toString());
p = p.revert();
console.log(p.toString());