on trigger exit, particle help (js)

what i am trying to do is emit a particle on trigger collision with the parent object and disable it on trigger exit.
i have a script that i wrote:

   function Start ( ) 
  {
     var child = transform.GetChild(0);
     child.particleEmitter.enabled = false; 
  }
  
 function OnTriggerStay(trigger : Collider) {
      if(trigger.gameObject.tag == "Water"){
          var child = transform.GetChild(0);
         child.particleEmitter.enabled = true; 
      }
 }

this by it’s self does not work and i am unsure on how to implement exit trigger.

any help/ amendments would be great

thanks

Enable the particle emitter when trigger is entered and disable it when trigger is exited.

// We better cache the child transform
var child : transform;

function Start ( ) 
{
	child = transform.GetChild(0);
	child.particleEmitter.enabled = false; 
}

function OnTriggerEnter(trigger : Collider) {
	if(trigger.gameObject.tag == "Water"){
		child.particleEmitter.enabled = true; 
	}
}

function OnTriggerExit(trigger : Collider) {
	if(trigger.gameObject.tag == "Water"){
		child.particleEmitter.enabled = false; 
	}
}