Javascript coding on how to zoom in using keyboard

Here's a simple javascript I put together. This uses vertical axis, which is W and S, as well as Up and Down Arrow Keys. Use these keys to zoom in and out. This uses Field of view to zoom in and out, keeping the camera in it's place. This script also has min and max zoom. Attach this script to the main camera in your scene.

 private var cam : Camera;
 var fov : float = 60f;
 var zoom_speed : float = 60.0f;
 var zoom_min : float = 30.0f;
 var zoom_max : float = 90.0f;
 
 function Start () 
 {
     cam = this.camera;
 }
 
 function Update () 
 {
     cam.fieldOfView = fov;
     
     if(fov >= zoom_max)
        fov = zoom_max;
     if(fov <= zoom_min)
        fov = zoom_min;
     if(Input.GetAxis("Vertical") > 0)
         fov+= zoom_speed * Time.smoothDeltaTime;
     else if(Input.GetAxis("Vertical") < 0)
         fov-= zoom_speed * Time.smoothDeltaTime;
         
 }