<script?type="text/javascript">???
function?count(){???????
????var?txt1?=?document.getElementById("txt1").value;???????
????var?txt2?=?document.getElementById("txt2").value;???????
????var?select?=?document.getElementById("select").value;???????
????var?kk?="";???????
????switch?(select)???????
????{????????
????????case?"+":???????????
????????????kk?=?txt1?+?txt2;???????????
????????????break;????????
????????????case?"-":????????????
????????????kk?=txt1?-?txt2;????????????
????????????break;????????
????????????case?"*":????????????
????????????kk?=?txt1?*?txt2'????????????
????????????break;????????
????????????case?"/":????????????
????????????kk?=txt1?/?txt2;????????????
????????????break;?????????
???????}???????
???????document.getElementById("fruit").value?=?kk;???
???????}??
???????</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()"?/>?<!--通過?=?按鈕來調用創建的函數，得到結果-->????
????????<input?type='text'?id='fruit'?/>????
????????</body>
2019-11-20
首先第15行【kk = txt1 * txt2 '】改為【kk = txt1 * txt2;】
其次如樓上所說要將獲取到的表單的值由字符串類型轉換為數值類型，用parseInt
2019-11-19
從txt1和txt2中取值是要用parseInt()轉換成數值?類型，如：var?txt1?=?parseInt(document.getElementById("txt1").value);