NameSpace player health

I have that code:

using UnityEngine;
using System.Collections;
using UnityEngine.UI;

public class HUD : MonoBehaviour

    public Sprite[] HeartSprites;

    public Image HeartUI;

    private Character character;

    void Start()
        character = GameObject.FindGameObjectsWithTag("Player").GetComponent<Player>();

and it sent me an error:
The type or namespace name `Character’ could not be found. Are you missing a using directive or an assembly reference?

My “Player” script was made in Javascript and called “Character”
What Can I do?
I’m making the health system from this tutorial: Unity 5 2D Platformer Tutorial - Part 13 - Player Health UI - YouTube

But All my scripts was made by me, and I didn’t make anything but Health from this tutorial

You’re mixing Javascript(unityscript) with c#, you need to ensure the .js code is compiled before the c# to resolve references. There are special folders for such occasions and are listed in the Unity3d Manual. Please place your .js code in one of the folders to ensure the type can resolve in c#.

Special Folders and Script Compilation Order

To the question of “where are these folders”, if they don’t exist… Create one from phase 1(like plugins) so the .js is build first resulting in them being available as types to the c# code.