How to add respawn to enemy AI?

I am creating a scenario where you have to fight off a certain enemy before he/she overwhelms you. If you don't do it fast enough the enemy takes over. Here is the script. I have tried many times, but the enemy won't respawn. I can make the "Player" respawn, however I can't seem to do it with the AI. Here is the script. I use Javascript. I placed the script on the enemy GameObject.

var spawnRange = 0.0; // the distance within which the enemy should be active. var gizmoName : String; // the type of the object. (See OnDrawGizmos() for more.) var enemyPrefab : GameObject; // link to the Prefab we'll be instantiating / destroying on demand.

// Cache variables, used to speed up the code. private var player : Transform; private var currentEnemy : GameObject; private var wasOutside = true;

// Called on Scene startup. Cache a link to the Player object. // (Uses the tagging system to locate him.) function Start () { player = GameObject.FindWithTag("Player").transform; }

// Called at least once every game cycle. This is where the fun stuff happens. function Update () { // how far away is the player? var distanceToPlayer = Vector3.Distance(transform.position, player.position);

// is he in range? if (distanceToPlayer < spawnRange) { // in range. Do we have an active enemy and the player has just come into range, instantiate the prefab at our location. if (!currentEnemy && wasOutside) currentEnemy = Instantiate(enemyPrefab, transform.position, transform.rotation);

 // player is now inside our range, so set the flag to prevent repeatedly instantiating the prefab.
 wasOutside = false;

 // ...and set our flag so we re-instantiate the prefab if the player returns.
 wasOutside = true;

}

}

// Called by the Unity Editor GUI every update cycle. // Draws an icon at our transform's location. The icon's filename is derived from the "type" variable, which allows this script to be used for any enemy. function OnDrawGizmos () { Gizmos.color = Color(1, 1, 1, 1);

// See the help docs for info on where the icon needs to be stored for this function to work.
Gizmos.DrawIcon(transform.position, gizmoName + ".psd");    

}

// Called by the Unity Editor GUI every update cycle, but only when the object is selected. // Draws a sphere showing spawnRange's setting visually. function OnDrawGizmosSelected () { Gizmos.color = Color(0, 1, 1); Gizmos.DrawWireSphere(transform.position, spawnRange); }

What am I doing wrong? Thanks to those that have helped me.