Asteroid Mini game. My problem is I can't stop my player object is still can moving out of the screen. and kept show null error.

function Update()
{
// Playe Movement and Speed axis

var transV : float = Input.GetAxis ("Vertical") * playerSpeedVertical * Time.deltaTime;
var transH : float = Input.GetAxis ("Horizontal") * playerSpeedHonrizontal *Time.deltaTime;	

transform.Translate (transH, transV, 0);

//When player is equal to x axis then stop the object if equal X

if (transform.postion.x >= 7)
	transform.postion.x = 7;

if (transform.postion.x <= -7)
		transform.postion.x = 7;

}

Can Someone plz kindly help me out of this? I am just a newbie to the Unity so I am also new to Java Script.
the Unity show Null error is following below:
NullReferenceException: Object reference not set to an instance of an object
Boo.Lang.Runtime.RuntimeServices.GetDispatcher (System.Object target, System.String cacheKeyName, System.Type cacheKeyTypes, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory)
Boo.Lang.Runtime.RuntimeServices.GetDispatcher (System.Object target, System.Object args, System.String cacheKeyName, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory)
Boo.Lang.Runtime.RuntimeServices.GetProperty (System.Object target, System.String name)
UnityScript.Lang.UnityRuntimeServices.GetProperty (System.Object target, System.String name)
player2Script.Update () (at Assets/player2Script.js:20)

What is ‘transform.postion’? I’ve not heard of that field before. Honestly, I’m amazed that it even compiles… Are you using #pragma strict? You should be. It’ll stop you from making mistakes like this one.

Change all your ‘transform.postion’ calls to ‘transform.position’, and next time make sure you check your spelling! Spelling is very important in programming.

sometimes the problem is simpler than we thought…

transform.postion.x = 7;

You are missing an I here… so it would be

transform.position.x = 7;

first correct the simplest and then we´ll continue