abstract-factory-example

////////////////////////////////////////////////////////////////////////////////////////////////////
// (Framework) Factory Module code

class Registry {
    constructor() {
        this.registry = { };
    }
    add(key, value) {
      this.registry[key] = value;
    }
    get(key) {
      return this.registry[key];
    }
}

class Factory {
  constructor(registry) {
    this.registry = registry;
  }

  throwException(msg, Type) {
    throw new Type(msg);
  }

  createInstance(classname) {
    var type;
      try {
        type = this.registry.get(classname).createInstance();
      } catch(err) {
        this.throwException("The type for \"" + classname + "\" isn't registered", TypeError);
      }

      if(type === undefined) {
        this.throwException("The type for \"" + classname + "\" isn't registered", TypeError);
      }

    return type;
  }
}

////////////////////////////////////////////////////////////////////////////////////////////////////
// (Framework) Transformations Module code

class NoTransformation { apply(str) { return str; } }
class NoTransformationFactory { createInstance() { return new NoTransformation(); } }

class Md5Transformation { apply(str) { return str.toUpperCase(); } }
class Md5TransformationFactory { createInstance() { return new Md5Transformation(); } }

class Rot13Transformation { apply(str) { return str.toLowerCase(); } }
class Rot13TransformationFactory { createInstance() { return new Rot13Transformation(); } }

var transformationsRegistry = new Registry();
transformationsRegistry.add('NoTransformation', new NoTransformationFactory());
transformationsRegistry.add('Md5', new Md5TransformationFactory());
transformationsRegistry.add('Rot13', new Rot13TransformationFactory());

var factory = new Factory(transformationsRegistry);

////////////////////////////////////////////////////////////////////////////////////////////////////
// Consumer/Project specific code

class Rot18Transformation { apply(str) { return str.replace('a', '..xx..'); } }
class Rot18TransformationFactory { createInstance() { return new Rot18Transformation(); } }

transformationsRegistry.add('Rot18', new Rot18TransformationFactory());

console.log(
    factory.createInstance('Md5').apply("abc"),                    // => Success
    factory.createInstance('Rot13').apply("aBc"),                   // => Success
    factory.createInstance('Rot18').apply("abc")                   // => Success
);