How to use OnTriggerEnter? (JS)

Ahoy,

This is a problem I have been dealing with for a while but never knew how to fix.

How do I get OnTriggerEnter to work?

In this script the player object has a rigidbody attached, so it should work, but absolutely no dice. I know it's kind of a noob question, but it's really bothering me since I need to finish this game for the GGJ 2015. The game is 2D, if that helps.

 var facingRight : boolean = true;
 var facingLeft : boolean = false;
 var jumped : boolean = false;
 var debug : boolean = false;
 var ground : Collider2D;
 
 function Update () {
 
     if (Input.GetKey(KeyCode.D)) {
         if (facingRight) {
             transform.Translate (0.1, 0, 0);
             facingRight = true;
             facingLeft = false;
         }
         if (facingLeft) {
             transform.Rotate (0, 180, 0);
             facingRight = true;
         }
     }
     
     if (Input.GetKey(KeyCode.A)) {
         if (facingLeft) {
             transform.Translate (0.1, 0, 0);
             facingLeft = true;
             facingRight = false;
         }
         if (facingRight) {
             transform.Rotate (0, 180, 0);
             facingLeft = true;
         }
     }
     
     if (Input.GetKeyDown(KeyCode.Space)) {
         if (jumped == false) {
             rigidbody2D.velocity = Vector2(0,6);
             jumped = true;
         }
     }
 }
 
 function OnTriggerStay (ground) {
 
     jumped = false;
     debug = true;
 }

Thanks.