麻烦老师查看作业，谢谢。

来源：4-14 项目作业

DanielDu87

2022-07-24 15:01:37

<!DOCTYPE html>
<html lang="zh">
   <head>
      <title></title>
   </head>
   <body>
      <input type="text" id="num1" />
      <select id="operate">
         <option value="+">+</option>
         <option value="-">-</option>
         <option value="*">*</option>
         <option value="/">/</option>
      </select>
      <input type="text" id="num2" />
      <input type="button" value=" = " id="btn" />
      <input type="text" id="result" />
      <script>
         window.onload = function () {
            var btn = document.getElementById("btn");
            btn.addEventListener("click",
               function () {
                  var opertor = document.getElementById("operate").value;
                  var ans = document.getElementById("result");
                  var num1 = parseFloat(document.getElementById("num1").value);
                  var num2 = parseFloat(document.getElementById("num2").value);
                  switch (opertor) {
                     case "+":
                        ans.value = (parseFloat(num1 + num2)).toString();
                        break;
                     case "-":
                        ans.value = (parseFloat(num1 - num2)).toString();
                        break;
                     case "*":
                        ans.value = (parseFloat(num1 * num2)).toString();
                        break;
                     case "/":
                        ans.value = (parseFloat(num1 / num2)).toString();
                        break;
                     default :
                        alert("error");
                  }
               },
               false);
         };
      </script>
   </body>
</html>

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