JS Mouselook script only works on one axis at a time?

I want to start by saying that I have next to no experience with Java, JavaScript, or Unity. I do, however, understand the basics, more or less, and was able to make a script for character movement with sprinting and stamina. What I've been working on next is a mouselook script. The problem I have is that only one axis will work at a time.

Code (JavaScript):

1.  
2. #pragma strict
3.  
4. public var Sensitivity : int = 3;
5. private var RotationY : short = 0.0;
6.  
7. function Update(){
8.     RotationY += Input.GetAxis("Mouse Y") * Sensitivity;
9.     transform.localRotation = Quaternion.AngleAxis (RotationY, Vector3.left);
10. }
11.  

This makes the up and down movement work fine.

Code (JavaScript):

1.  
2. #pragma strict
3.  
4. public var Sensitivity : int = 3;
5. private var RotationY : short = 0.0;
6. private var RotationX : short = 0.0;
7.  
8. function Update(){
9.     RotationY += Input.GetAxis("Mouse Y") * Sensitivity;
10.     transform.localRotation = Quaternion.AngleAxis (RotationY, Vector3.left);
11.  
12.     RotationX += Input.GetAxis("Mouse X") * Sensitivity;
13.     transform.localRotation = Quaternion.AngleAxis (RotationX, Vector3.up);
14. }
15.  

This only makes the side-to-side axis rotate.

I'm sure i'm missing something stupidly obvious to anyone who knows what they're doing. Please help.

 

You have overwritten the localRotation each time. You need to combine both rotations before assigning to localRotation.

 

How exactly do I do that?