<script>
?????function?getSum(x)?{???
????????if(x?==?1){
????????????return?1;
????????}else{
????????????return?x*getSum(x-1);
????????}
????}
????var?i;
????i?=?prompt("請(qǐng)輸入一個(gè)求階乘的數(shù)：")
????while(i?==?''?||?isNaN(i)?||?i?==?"?"){
????????alert("輸入錯(cuò)誤，請(qǐng)重新輸入！");
????????i?=?prompt("請(qǐng)輸入一個(gè)求階乘的數(shù)：")
????}
????if(i?==?0){
????????alert("0的階乘是：0")
????}
????getSum(i);
????alert(i+"的階乘是："+getSum(i));
????</script>
