Mein Fehler?

<script>
x = window.prompt("Wie lang???","0")
</script> <script type='text/javascript'>
h = x
m = 0
n = 0
g = 0
b = 0
s = 0
StartEndeUhr(){
setInterval("time()",1000);
}
</script> <script type='text/javascript'>
time(){
if (h < 61)
document.getElementById("anzeige").firstChild.nodeValue = "Der Counter läuft noch " + h + " Stunden, " + m + " Minuten und " + n + " Sekunden!";
var n = n - 1;
if (n == 0)
var m = m - 1
var n = 59;
if (m == 0 && n == 0)
var h = h - 1
var m = 59
var n = 59;
if (h == 0 && m == 0 && n == 0)
document.getElementById("anzeige").firstChild.nodeValue = "Beendet!;
}
</script>  <input type="button" onclick="StartEndeUhr()" value="Loszählen!" name=" Counter_Go " />
<p id="anzeige">ZEIT</p>

<script type="text/javascript">
   var x = window.prompt("Wie lang???","0");
   var h = x;
   var m = 0;
   var n = 0;
   var g = 0;
   var b = 0;
   var s = 0;
   
   function StartEndeUhr() {
      setInterval("time()",1000);
   }
   
   function time() {
   if (h < 61)
      document.getElementById("anzeige").innerHTML = "Der Counter läuft noch " + h + " Stunden, " + m + " Minuten und " + n + " Sekunden!";
      n = n - 1;
      if (n == 0) {
         m = m - 1;
         n = 59;
      }
      if (m == 0 && n == 0) {
         h = h - 1;
         m = 59;
         n = 59;
      }
      if (h == 0 && m == 0 && n == 0) {
         document.getElementById("anzeige").innerHTML = "Beendet!";
      }
   }
</script>

<input type="button" onclick="StartEndeUhr()" value="Loszählen!" name=" Counter_Go " />
<p id="anzeige">ZEIT</p>