Toggle map/Camera [JS]

Hey guys, I decently new to java-script+unity and I recently have been fooling around and trying to figure out how things work and I recently started on making a game to help refine and learn some of the java-script coding and to get use to unity.

Anyways, I recently wanted to learn how to change cameras with a key-press and successfully figured out how to make it enable and disabled cameras with two different keys but how would I make it so that it changes the cameras with only one key(holding the key down or having to press it two times to disable the map camera again).

I tried a few things but couldn't figure it out but here is the last code I was using:

 var camera1 : GameObject;
 var camera2 : GameObject;
 var mKeyDown : boolean = false;
 
 function Start () {
    camera1.camera.enabled = true;
    camera2.camera.enabled = false;
 
 }
 
 function Update(){
 
 if(Input.GetKeyDown("m")){
     mKeyDown = true;
     camera1.camera.enabled = false;
     camera2.camera.enabled = true;
     }
 
 if(Input.GetKeyDown("m")){
     mKeyDown = false;
     camera2.camera.enabled = false;
     camera1.camera.enabled = true;
     }
 }

I know I'm missing something big, but I don't really know what.