class ballBehavior extends Sup.Behavior{
    
    private ballActor: Sup.Actor;
    private ballAngle: number;
    private ballPosition: Sup.Math.Vector3;
    private ballVelocity: number;
    
    constructor(ball) {
        super(ball);
        this.ballActor = new Sup.Actor("Ball");
        this.ballActor.setPosition(0, 0, 0);
        this.ballAngle = 0;
        this.ballPosition = new Sup.Math.Vector3;
        this.ballVelocity = 0;
        this.ballActor.addBehavior(ballBehavior);
    }
    
    update(){
        this.ballAngle += this.ballVelocity;
        
        //Constrains the angle between 0 and 2pi
        if(this.ballAngle > Math.PI * 2) this.ballAngle = 0 + this.ballAngle - Math.PI * 2;
        }else if (this.ballAngle < 0) this.ballAngle = Math.PI - this.ballAngle + Math.PI * 2;
        
        //Maybe a little spinback on the pointer?
        this.ballPosition = new Sup.Math.Vector3(Math.cos(this.ballAngle) * wheelActor.getLocalScaleX() * 100 / 100, Math.sin(this.ballAngle) * wheelActor.getLocalScaleX() * 100 / 100, 0);
            
        if(Sup.Input.wasKeyJustPressed("LEFT")) this.ballVelocity = 0.5;
    }
}

dont declare all variables into constructor, always on top of this

Also, how would one be able to call on properties stored in an actor's behavior? Like, if I wanted to grab the velocity from an object's behavior and that property was public, how would I reference it? Calling Sup.Actor.getBehavior just returns the class itself, not the instance of the class that I'm trying to refer to.

All of the properties in a behavior class can be accessed from within itself by using "this.propertyName". The actor it belongs to can be accessed with "this.actor". If you want a more advanced way of setting up an actor when created, you can add awake() which happens instantly, or start() which happens in the next "tick" of game logic. They are used in the same way update() is, but only called once.

class ballBehavior extends Sup.Behavior{
    private angle: number = 0;
    private position: Sup.Math.Vector3 = new Sup.Math.Vector3();
    private velocity: number = 0;

    awake() {
        // You can add code here that will be called only once when it's created.
    }

    update(){
        this.angle += this.velocity;
        
        //Constrains the angle between 0 and 2pi
        if(this.angle > Math.PI * 2) this.angle = 0 + this.angle - Math.PI * 2;
        }else if (this.angle < 0) this.angle = Math.PI - this.angle + Math.PI * 2;
        
        //Maybe a little spinback on the pointer?
        this.position = new Sup.Math.Vector3(Math.cos(this.angle) * wheelActor.getLocalScaleX() * 100 / 100, Math.sin(this.angle) * wheelActor.getLocalScaleX() * 100 / 100, 0);
            
        if(Sup.Input.wasKeyJustPressed("LEFT")) this.velocity = 0.5;
    }
}

If you want to create an actor with a behavior, you just need to use addBehavior() to give it one. You can even change it's default properties too.

// Create a new ball with a behavior.
new Sup.Actor("Ball").addBehavior(ballBehavior);

// Create a new ball with a behavior that starts with altered properties. (almost like a constructor, but every property is optional)
new Sup.Actor("Ball").addBehavior(ballBehavior, {
    angle: Math.PI,
    position: new Sup.Math.Vector3(2, 2, 2),
    velocity: 10
});

// Create a new ball with a behavior that has a different velocity. (properties are optional, so you only need to change the ones you want)
new Sup.Actor("Ball").addBehavior(ballBehavior, {velocity: 10});

If you want to modify the properties after creation, getBehavior() allows you to access the properties in an actor.

// You can do something like this...
let actor = Sup.getActor("Ball");
actor.getBehavior(ballBehavior).velocity = 0;

// Or this...
let actor = Sup.getActor("Ball").getBehavior(ballBehavior);
actor.velocity = 0;

Hope this helps! :)