How can I improve this code?

This is a javascript script that spawns certain objects based on what number the timer starts and spawns the objects every x seconds in 2 different locations. For some reason this code keeps crashing my macbook so it's really annoying and I don't know how to improve it better because I am fairly new to javascript. Here is the script:

   #pragma strict
     
     var spawning : boolean = false;
     var spawn1 : Transform;
     var spawn2 : Transform;
     var timer : float;
     var green : Rigidbody[];
     var build : Rigidbody[];
     var buildr : Rigidbody[];////for objects on the right
     var index : int;
     var indexr : int;
     var whatSpawn: float;///what objects to start spawning
     var objgreen : Rigidbody;
      var objbuild : Rigidbody;
      var objbuildr : Rigidbody;
      
     public static var picker : int;///used in objects moving script
     
     function Start(){
     
     whatSpawn = Mathf.Abs(Random.Range(0,60));
     }
     function FixedUpdate ()
     {
     whatSpawn += Time.deltaTime;
      if(!spawning){
       timer += Time.deltaTime;
      }
      if(timer >= 0.5f){
       Spawn();
      }
     }
      
     function Spawn()
 {
      spawning = true;
      timer = 0;
      var randomPick : int = Mathf.Abs(Random.Range(0,3));///decides where objects will spawn
      var location : Transform ;
 
     if(randomPick == 1 ){
       location = spawn1;
       picker = 1;
     
      }
      else if(randomPick == 2 ){
       location = spawn2;
       picker = 2;
      }
      
     
     if(spawning == true){
          
          if(whatSpawn > 0 && whatSpawn < 20 ){
          index = Random.Range (0, green.Length );
          objgreen = green[index];
          objgreen =  Instantiate(objgreen,location.position,location.rotation);
         objgreen.AddForce(Vector3(0,0,100));
          }
      
       if(whatSpawn > 20 ){
               index = Random.Range (0, build.Length);
               indexr = Random.Range (0, buildr.Length);
            objbuild  = build[index];
           objbuildr  = buildr[indexr];
          objbuild =  Instantiate(objbuild,spawn1.position,spawn1.rotation);
         objbuildr =  Instantiate(objbuilds,spawn2.position,spawn2.rotation);
           }
           if(whatSpawn >= 40){//////dont let whatSpawn go over 40
           gren = 0;
           }
       }
      //halt script for 1 second before returning to the start of the process
      //set spawning back to false so timer may start again
      spawning = false;
     }