Increase a variable of an other script

scriptname.variablename works only with static variables. With standard public variables you need to first get the object, then the componentn and then you can edit the variables.

I had this problem too. This was my solution.

The first script, I made my portrait layout for things like Health, Ammo, etc.(I am including only what is necessary. The first file is called Portrait.js)

     public var ammo;
     var usedammo;
     
                 ammo = 100;
  usedammo = 0;
  remainingammo = ammo*1;
 
 function OnGUI(){
 
  GUI.Label(Rect(480,Screen.height-45,80,75),"Ammo:", ammofont);
     }
     if(ammo <= 10){
 
 function Update(){
  if(ammo >= 0){
  reloadfont.normal.textColor = Color.yellow;
  GUI.Label(Rect(Screen.width-760,Screen.height-500,750,30), "Low Ammo", reloadfont);
  }
  }
     }

This is the second script, Shoot.js

 var bullet : Rigidbody; 
 var speed : float = 10.0f;
 var muzzlePoint : Transform;
 
 var getammo;
 getammo = GameObject.FindWithTag("Portrait").GetComponent(portrait);
 Debug.Log(getammo); 
 
 function Update() {
     if(Input.GetButtonDown("Fire1")) {
      if(getammo.ammo > 0){
      if(Time.timeScale == 1){
      bullet.useGravity = false;
         var instance : Rigidbody = Instantiate(bullet, muzzlePoint.position, Quaternion.identity);
         instance.velocity = muzzlePoint.forward * 100;
         }
         }
     }
 }

What this does, is allows you to call a variable outside of the current script, using

 GameObject.FindWithTag("objectag")GetComponent("otherscript.js");

My first variable:

 getammo

This brings the first .js file into the scripting. To use it, all I do is:

 getammo.otherscriptvariable

That's all there is to it. Hope this helped.