Ground Check confusion with Triggers

Hi, I'm not a programmer, but I would like some help on making triggers for my project. See, I have triggers for a ground check on my objects and in the script they all have to be variables.

 var BallRigid:Rigidbody;
 var Ball:Collider;
 var isGrounded : boolean = false;
 var speed = 40.0; 

 function Update () {      
 var cameraTransform = Camera.main.transform; 

  
 var forward = cameraTransform.TransformDirection(Vector3.forward); 
 forward.y = 0; 
 forward = forward.normalized; 
   
 var right = Vector3(forward.z, 0, -forward.x); 

 if (Input.GetKey ("w")) { 
     rigidbody.AddForce(forward * speed * (Time.deltaTime* Acceleration)); 
 } 

 if (Input.GetKey("s")) { 
     rigidbody.AddForce(forward * -speed * (Time.deltaTime*Acceleration)); 
 } 
 
 if (Input.GetKey ("a")) { 
     rigidbody.AddForce(right * -speed * (Time.deltaTime*Acceleration)); 
 } 

 if (Input.GetKey ("d")) { 
     rigidbody.AddForce(right * speed * (Time.deltaTime* Acceleration)); 
 } 

 if (isGrounded){
     if (Input.GetButtonDown ("Jump")) {
         rigidbody.velocity = rigidbody.velocity + Vector3 (0,Jump,0); 
     }
 }
 if (Input.GetKey ("r")){
     BallRigid.transform.position.x = 0;
     BallRigid.transform.position.y = 0;
     BallRigid.transform.position.z = 0;
     BallRigid.rigidbody.velocity = Vector3 (0,0,0);
 }
 }

 function OnTriggerStay () {isGrounded = true;}

 function OnTriggerExit () {isGrounded = false;}

That's the script I use for the movement and ground check of my Marble/Ball in the game. Everything works but I have to declare every single thing that I can jump off of. Is there an easier way to do this with tags or the same variable for multiple objects or something like that? Thanks.