JavaScript 简易网页计算器实现

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<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>计算器</title>
<script language="javascript">

 var oper1=prompt("请输入第一个操作数：");
 var oper2=prompt("请输入第二个操作数：");
 var operator=prompt("请输入运算符（+，-，*，/）");
 parse();
 var result;
 switch(operator)
 {
  case"+":
   result=doSum(oper1,oper2);
   alert(oper1+"+"+oper2+"="+result);
   break;
  case"-":
   result=doSubstract(oper1,oper2);
   alert(oper1+"-"+oper2+"="+result);
   break;
  case"*":
   result=doMultiply(oper1,oper2);
   alert(oper1+"*"+oper2+"="+result);
   break;
  case"/":
   result=doDivide(oper1,oper2);
   alert(oper1+"/"+oper2+"="+result);
   break;
  default:
   alert("输入的运算符不合法");
  }
  function parse(){
   if(isNaN(oper1)||isNaN(oper2)){
    alert("输入的数字不合法");
    }
   else{
    oper1=parseFloat(oper1);
    oper2=parseFloat(oper2);
    }
   }
  function doSum(oper1,oper2){
   return oper1+oper2;
   }
  function doSubstract(oper1,oper2){
   return oper1-oper2;
   }
  function doMultiply(oper1,oper2){
   return oper1*oper2;
   }
  function doDivide(oper1,oper2){
   return oper1/oper2;
   }
</script>
</head>

<body>
</body>
</html>