Countdown with minutes and seconds?

I am new to scripting and i am really struggling to find a script or create one for a box in the top right hand corner of the screen which is a countdown timer in minutes and seconds. It is possible to do this in javascript?

This should do the trick, it will start at the beginning of the scene it is in. Sorry, only just saw you requested JavaScript but i believe this very simple code should be easy to translate, if you need help just ask.

   using UnityEngine;
    using System.Collections;
    using UnityEngine.UI;
    public class CountDownTimer : MonoBehaviour {
        float TimeAtStartOfScene;  // when the timer begins
        float CountDownValue;
        float CountDownLength; // how long the time will countdown for
        public Text txt; // attach to UI text in the scene to display time
    	
        // Use this for initialization
    	void Start () {
            txt.transform.position = new Vector3(0, 0, 0);
            // set the position, in your case it would be the top right of the screen
            TimeAtStartOfScene = Time.time;
            // get the time at the start of the scene, when the countdown shall begin
            CountDownLength = 60; // 1 min countdown length
    	}
    	
    	// Update is called once per frame
    	void Update () {
            CountDownValue = (TimeAtStartOfScene + CountDownLength) - (Time.time - TimeAtStartOfScene);
            // update the countdown value (you may wish to round it)
            txt.text = "" + CountDownValue;
            // set the countdown value
    	}
    }