How do I put a texture on my Cube using code (JavaScript)

I am completely new to Unity 3D. I own the free version. For my first project, I am trying to make a MineCraft like clone. I followed tutorials, but now i'm trying to change something so it works how I want it. First off, how can I place a cube with a texture on it? Here's a chunk of code where I need to be able to do this:

 function Build() { 
     if (HitBlock()) { 
         var cube = GameObject.CreatePrimitive(PrimitiveType.Cube); 
         cube.transform.position = hit.transform.position + hit.normal; 
     } 
 }
 

This spawns a default cube with no texture whatsoever. How do I get a texture?

Here is my entire code ( I followed tutorials, so I shouldn't be saying mine):

 var blockLayer : LayerMask = 1; 
 var range : float = Mathf.Infinity; 
 var hit : RaycastHit;
 
 function Update () { 
     if (Input.GetMouseButtonDown(1)) Build(); 
     if (Input.GetMouseButtonDown(0)) Erase(); 
 }
 
 function Build() { 
     if (HitBlock()) { 
         var cube = GameObject.CreatePrimitive(PrimitiveType.Cube); 
         renderer.material.mainTexture = Resources.Load("Dirt.png");
         cube.transform.position = hit.transform.position + hit.normal; 
     } 
 }
 
 function Erase() { 
     if (HitBlock()) 
     Destroy(hit.transform.gameObject); 
 }
 
 function HitBlock() : boolean { 
     return Physics.Raycast(transform.position, transform.forward, hit, range, blockLayer); 
 }