简易计算机JS代码编译@慕课网原创_慕课网

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

   }
  </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()"/> <!--通过 = 按钮来调用创建的函数，得到结果--> 
   <input type='text' id='fruit' />   
 </body>
</html>