                        课程
                    
                        /前端开发
                        
                            /JavaScript
                        
                        /JavaScript进阶篇

实现不了到底哪错了呢？

<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
   function count(){
    var txt1 = document.getElementById("txt1").value;
    var txt2 = document.getElementById("txt2").value;
    var c= document.getElementById("select").value;
    var result = "";
    switch(c) {
        case "+":
            result = parseInt(txt1) + parseInt(txt2);
            break;
        case "-":
            result = parseInt(txt1) - parseInt(txt2);
            break;
        case "*":
            result = parseInt(txt1) * parseInt(txt2);
            break;
        default:
            result = parseInt(txt1) / parseInt(txt2);
    }
    document.getElementById("fruit").value = result;
</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>