mymoney = 0;
do{
var num = parseInt(prompt('请输入您的操作:\n'+'1.存钱\n'+'2.取钱\n'+'3.显示余额\n'+'4.退出'));
switch(num){
case 1:
var money = parseFloat(prompt('请输入存的钱数'));
mymoney = mymoney + money;
alert('你现在的钱数是'+mymoney+'元');
break;
case 2:
var gomoney = parseFloat(prompt('请输取出的钱数'));
if(mymoney - gomoney >= 0){
mymoney = mymoney - gomoney;
alert('你现在的钱数是'+mymoney+'元');}else{alert('余额不足')}
break;
case 3:
alert('你现在的钱数是'+mymoney+'元');
break;
case 4:
break;
default:
alert('输入有误,请按规定输入');
}}while(num != 4)
alert('正在退出.....')