Expression property type
The Expression type is the way you have to create a property of any type. You can use any type for the values and any JavaScript expression for setting the values. For example, you can use it to create a property to reference an event handler (or callback function):
The scene compiler generates Expression properties like this:
class Dragon extends Phaser.GameObjects.Sprite {
constructor(..) {
...
}
/** @type {(obj:Dragon)=>void} */
onClickHandler = obj => {};
}