                        課程
                    
                        /前端開發
                        
                            /JavaScript
                        
                        /JavaScript進階篇

感覺自己這個沒有錯啊

<html>
?<head>
? <title> 事件</title> ?
? <script type="text/javascript">
?? function count(){
?? ?
?? //獲取第一個輸入框的值
??? var ToTxt1=document.getElementById("txt1").value;
?? ?//獲取第二個輸入框的值
??? var ToTxt2=document.getElementById("txt2").value;
?? ?//獲取選擇框的值
??? var ToSelect=document.getElementById("select").value;
?? ?//獲取通過下拉框來選擇的值來改變加減乘除的運算法則
??? var sum = "";
??? switch(ToSelect)
??? case "+":
?????? sum = parseInt(ToTxt1) + parseInt(ToTxt2);
?????? break;
??? case "-":
?????? sum = parseInt(ToTxt1) - parseInt(ToTxt2);
?????? break;
??? case "*":
?????? sum = parseInt(ToTxt1) * parseInt(ToTxt2);
?????? break;
??? default:
?????? sum = parseInt(ToTxt1) / parseInt(ToTxt2);
??? }
??? //設置結果輸入框的值
??? document.getElementById("fruit").value = sum;
?? }
? </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>