JS设置一定数字范围产生随机数代码

<SCRIPT LANGUAGE="JavaScript">
<!-- Begin
function numbers() {
var nummenu = document.lotto.numbercount;
var numbercount = nummenu.options[nummenu.selectedIndex].value*1;
var maxnumbers = document.lotto.maxnum.value*1;
if (numbercount > maxnumbers) {
alert("Be sure to select a max lottery number value!");
}
else {
var ok = 1;
r = new Array (numbercount);
for (var i = 1; i <= numbercount; i++) {
r[i] = Math.round(Math.random() * (maxnumbers-1))+1;
}
for (var i = numbercount; i >= 1; i--) {
for (var j = numbercount; j >= 1; j--) {
if ((i != j) && (r[i] == r[j])) ok = 0;
   }   
}
if (ok) {
var output = "";
for (var k = 1; k <= numbercount; k++) {
output += "Number " + k + " = " + r[k] + "\n";
}
document.lotto.results.value = output;
}     
else numbers();
   }
}
//  End -->
</script>
<form name="lotto">
<table width=100% border=0>
<tr>
<td align=center>产生数字个数
<select name="numbercount">
<option value="1">1
<option value="2">2
<option value="3">3
<option value="4">4
<option value="5">5
<option value="6" selected>6
<option value="7">7
<option value="8">8
<option value="9">9
<option value="10">10
</select>  
<br>产生数字范围<input type=text name=maxnum value="31" size=2 maxlength=2><br>
<input type=button value="产生随机数" onClick="numbers()">
<p>
<textarea name="results" rows=11 cols=15></textarea>
</td>
</tr>
</table>
</form>