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):

Expression property declaration.

The scene compiler generates Expression properties like this:

class Dragon extends Phaser.GameObjects.Sprite {

    constructor(..) {

    /** @type {(obj:Dragon)=>void} */
    onClickHandler = obj => {};