Javascript dynamic type system decorator

typeDecorator.js

const typeDecorator = (type) =>
  (target, key, descriptor) => {
    let value;
    return {
      enumerable: true,
      get: function () { return value; },
      set: function (newValue) {
        const newType = typeof newValue;

        if (newType !== type || newType === 'undefined') {
          const error = `invalid type for "${key}", expect "${type}" but get "${newType}"`;
          throw Error(error);
        }

        value = newValue;
      }
    }
  }