个回答

• 木畏

  2015-04-03 16:00:16

  参考了一下楼上大神的，再对比一下您的，我发现你没有声明result

  0

• 康振宁

  2015-04-03 14:01:56

  两种解决方案：

  一、

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

  二、

  <script type="text/javascript">
      function count(){   
          var a=document.getElementById("txt1").value;
          var b=document.getElementById("txt2").value;
          var c=document.getElementById("select").value;
          var result=0;
          switch(c){
              case "+":
                  result=parseInt(a)+parseInt(b);
                  break;
              case "-":
                  result=parseInt(a)-parseInt(b);
                  break;
              case "*":
                  result=parseInt(a)*parseInt(b);
                  break;
              default:
                  result=parseInt(a)/parseInt(b);
                  break;
          }
          document.getElementById("fruit").value = result;
      }
  </script>

  你应该看完代码后就能明白自己错在哪里了

  0