<html>
<head>
<title>判断素数</title>
</head>
<script>
var N;
N = parseInt(prompt("N=",""));
var flag = 0;
for(var j=2;j < N;j++){
if(N%j==0){
flag = 1;
}
break;
}
if(flag)
{
alert(N+":Composite");
}
else{
alert(N+":Prime");
}
</script>
<body>
</body>
</html>
原文：http://www.cnblogs.com/ink-grass/p/5451109.html