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                        /JavaScript进阶篇

各位大神能帮我找下错误吗？还是无法运行

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

    //获取第一个输入框的值
    var shu1 = parseInt(document.getElementById('txt1').value);

   //获取第二个输入框的值
   var shu2 = parseInt(document.getElementById('txt2').value);

   //获取选择框的值
   var fu = document.getElementById('select').value;

   //获取通过下拉框来选择的值来改变加减乘除的运算法则
   var final ='';
   swich (fu){

       case '+' :
       fianl = shu1 + shu2;
       break;
       case '-' :
        final = shu1 - shu2;
        break;
        case '*' :
        fianl = shu1 * shu2;
        break;
        case '/' :
       final = shu1 / shu2;
       break;
   }


    //设置结果输入框的值
    document.getElementById("fruit").value = final;

   }
</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>