Cannot access js script from cs script

,This I think might be the problem (cs > js). Because it’s the only thing in which differs my script of the script in tutorial. It is error here: "error CS0246: The type or namespace name ‘BallControl3D’ could not be found… " Here is the script:

using UnityEngine;

public class JumpButton : MonoBehaviour {

    public GameObject player;
    private BallControl3D script;

    private void Awake()
        player = GameObject.FindGameObjectWithTag("Player");        
        script = player.GetComponent<BallControl3D>();

    void OnMouseDown()

UnityScript (Unity’s Javascript variant) is obsolete and no longer supported in the latest Unity versions. So if BallControl3D is a UnityScript script you need to recreate / port it to C#.