Having scripts interact

There are 3 ways to access other script members:

-|-Static, make the variable static and you can access it with the scriptname and the var name

Player.js

 static var health:int;

anywhere:

 Player.health-= damage;

Pros: Easy to use. Cons: Static means only one instance of the variable exists, meaning that if you have a static for enemy health, they all die at once. It is fine though for player health, player score, enemy counts or anything that is only once in the game.

-|-GetComponent, you can access other script with GetComponent like this:

 var other : ScriptName;
 other = gameObject.GetComponent("ScriptName");
 other.someVariable = 5;

Better is to cache if the action is used often

 var other : ScriptName;
 function Start(){
 other = gameObject.GetComponent("ScriptName");}
 
 function Update(){
 other.someVariable = 5;}

if the script belongs to another object:

 var other : ScriptName;
 function Start(){
 other = GameObject.Find("ObjectName").GetComponent("ScriptName");}
 
 function Update(){
 other.someVariable = 5;}

Pros:works for all variables and functions of any types (or almost). Cons: takes a little work and understanding at first. A little exepensive if not cached.

-|-SendMessage(), you can simply send a message to an obejct to tell him what to do.

anywhere

 GameObject.Find("OtherObject").SendMessage ("Dosomething");
 //If the script is on the same object(gameObject. is actually not compulsory)
 gameObject.SendMessage ("Dosomething");

another script

 function Dosomething(){
 //Do smg;}

if the function requires parameter, they are passed in the parenthesis as such:

 GameObject.Find("OtherObject").SendMessage ("Dosomething",10,20);

 function Dosomething(a:int, b:int):int{
 return a + b;}

Pros:quite easy to use and straightforward. Cons: Really expensive, not to be used when the action is repeated.

-|-BroadcastMessage(), works the same as SendMessage(). BM sends the message to the object and all children of the object. If they all hold a script everyone will react. SM only affect the targeted object.

Pros and cons are similar to SendMessage except cons are multiplied by the amount of children.

EDIT: I added cases for GetComponent and SendMessage when the script is on another object and Broadcast Message.