When receiving a Config object, the typical things a constructor does is:

In TypeScript code, this could be done like this:

 constructor(config: Config<MyClass>) {
  super(Object.assign(Config<MyClass>({
    id: "4711",
    configOption1: "bar",
    configOption2: [42, 24]
  }), config));
} 

However, there is a special utility class named ConfigUtils (formerly in ActionScript: Exml) that helps implementing a specific merge logic. For array-valued properties, it should be possible to instead of replacing the whole array, append or prepend to the existing value. The concrete use cases where this often makes sense are Ext component's plugins and items properties. So at least if your class has any array-valued properties, in your constructor, you should use the following:

 import ConfigUtils from "@jangaroo/runtime/ConfigUtils";
...
    constructor(config: Config<MyClass>) {
      super(ConfigUtils.apply(Config<MyClass>({
        id: "4711",
        configOption1: "bar",
        configOption2: [42, 24]
      }), config));
    } 

Any client using such a component can then use

import ConfigUtils from "@jangaroo/runtime/ConfigUtils";
...
      Config(MyClass, {
        id: "4711",
        configOption1: "bar",
        ...ConfigUtils.append({
          configOption2: [12]
        }
      }), config));
    }

The resulting value of configOption2 after merging via ConfigUtils.apply() will be [42, 24, 12]. There is an analogous utility method ConfigUtils.prepend(). Both return an object, handing through the given property, complementing it by an internal marker property that specifies where to insert the value into the previous value. To "lift" these properties into surrounding object code, the spread operator ... is used.