Hold touch button Unity Javascript

I have script for crouching when i press and hold S its crouching when i release the button the player gets in his normal size. Now i want to do the same thing with touch button but i cant figure how to do that, can some1 help?

  static var vScale = 1.0;
  private var tr: Transform;
  private var dist: float; // distance to ground
 
  function Start(){
      tr = transform;    
      var ch:CharacterController = GetComponent(CharacterController);
      dist = ch.height/2; // calculate distance to ground
  }
 
  function Update()
  {
 
      vScale = 1.0;s 
      if (Input.GetKey("s")){ // press s to crouch
          vScale = 0.5;
      }
      var ultScale = tr.localScale.y; // crouch/stand up smoothly 
      tr.localScale.y = Mathf.Lerp(tr.localScale.y, vScale, 5*Time.deltaTime);
      tr.position.y += dist * (tr.localScale.y-ultScale); // fix vertical position
   }
       function OnGUI ()
     { 
 }