                        課程
                    
                        /前端開發
                        
                            /JavaScript
                        
                        /JavaScript進階篇

大神們能幫我看看哪里出問題了嗎

<!DOCTYPE?html>
<html>
?<head>
??<title>?事件</title>??
??<script?type="text/javascript">
???function?count(){
?????var?result="";
?????var?x1?=?document.getElementById("tx1").value;
?????var?x2?=?document.getElementById("tx2").value;?
?????var?x3?=?document.getElementById("select").value;?
?????switch?(x3){
?????????case?"+"?:
?????????????result=parseInt(x1)+parseInt(x2);
?????????case?"-"?:
?????????????result=parseInt(x1)-parseInt(x2);
?????????case?"*"?:
?????????????result=parseInt(x1)*parseInt(x2);
?????????case?"/"?:
?????????????result=parseInt(x1)/parseInt(x2);
?????}
??????document.getElementById("fruit").value=result;??
????//獲取第一個輸入框的值
	//獲取第二個輸入框的值
	//獲取選擇框的值
	//獲取通過下拉框來選擇的值來改變加減乘除的運算法則
????//設置結果輸入框的值?
???}
??</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>
</html>