个回答

• 黄璞

  2016-06-28 15:56:31

  已采纳

  document.getElementById("txt1").value 获取的值为字符串 需要用parseInt()函数解析字符串为整数,如果不能解析会返回 NaN,  所以你获取文本框的值后 还需要转换 ,如下代码这么写:parseInt(document.getElementById("txt1").value);

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• qq_主流革新ZG_03388100

  2016-06-28 15:16:49

   <script type="text/javascript">
     function count(){
         var otxt1=document.getElementById("txt1").value;
         var otxt2=document.getElementById("txt2").value;
         var oselect=document.getElementById("select").value;
         var result="";
         switch(oselect)
         {
             case "+":
             result=otxt1+otxt2;
             break;
             case"-":
             result=otxt1-otxt2;
             break;
             case"*":
             result=otxt1*otxt2;
             break;
             default:
             result=otxt1/otxt2;
         }
      document.getElementById("fruit").value=result;
      
     }
    </script>

  
  

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