求帮忙，哪里错了喃，就是运行不出来-慕课网

求帮忙，哪里错了喃，就是运行不出来

来源：6-11 编程练习

慕粉3287797

2016-05-01 15:54

<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
   function count(){

    var num1=document.getElementById("txt1").value;
    var num1=document.getElementById("txt2").value;
    var str=document.getElementById("select").value;
    var str1="";
    switch (str){
        case "+":
            str1=parseFloat(num1) + parseFloat(num2);
            break;
        case "-":
            str1=parseFloat(num1) - parseFloat(num2);
            break;
        case "*":
            str1=parseFloat(num1) * parseFloat(num2);
            break;
        case "/":
            str1=parseFloat(num1) / parseFloat(num2);
            break;
    }
    document.getElementById("fruit").value = str1;
   }
</script>
</head>
<body>

   <input type="text" id="txt1" />
   <select id="select">
        <option value="+">+</option>
       <option value="-">-</option>
       <option value="*">*</option>
       <option value="/">/</option>
   </select>
   <input type="text" id="txt2" />
   <input type="button" value=" = " onclick="count()" /> 
   <input type="text" id="fruit" />

</body>
</html>