Javascript Stateful

stateful_with_proxy.js

Stateful = {
  extend: function(klass) {
    var currentState = klass.prototype;
    var states = {null: currentState};

    klass.prototype.gotoState = function(stateName, ...args) {
      currentState = states[stateName];
    }

    klass.addState = function(stateName, state) {
      states[stateName] = state;
    }

    return new Proxy(klass, {
      construct: function(target, args) {
        var instance = Reflect.construct(target, args);
        return new Proxy(instance, {
          get: function(target, name, receiver) {
            if (currentState[name]) {
              return currentState[name];
            } else {
              return target[name];
            }
          }
        });
      }
    });
  }
}

function Test(foo) {
  this.foo = foo;
  this.test = 1;
}
var states = {};
var currentState = Object.assign({}, Test.prototype);
Test.prototype.gotoState = function(stateName, ...args) {
  currentState = states[stateName];
}
Test.addState = function(stateName, state) {
  states[stateName] = state;
}

Test.addState("TestState", {
  foo: 'test state bar'
})

t = new Test("bar");
p = new Proxy(t, {
  get: function(target, name, receiver) {
    if (currentState[name]) {
      return currentState[name];
    } else {
      return target[name];
    }
  }
});