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                        /JavaScript進階篇

運行不出來，檢查不出錯誤在哪，求幫忙

<!DOCTYPE?html>
<html>
?<head>
??<title>?事件</title>??
??<script?type="text/javascript">
???function?count(){
???var?result?=?"";??
????//獲取第一個輸入框的值
????var?num1=document.getElementById("txt1").value;
	//獲取第二個輸入框的值
????var?num2=document.getElementById("txt2").value;
	//獲取選擇框的值
????var?c=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
????switch(c){
????????case?'+':
		result=parseFloat(num1)?+?parseFloat(num2);
		break;
????????case?"-":
		result=parseFloat(num1)?-?parseFloat(num2);
		break;
????????case?"*":
		result=parseFloat(num1)?*?parseFloat(num2);
		break;
????????default:
		result=parseFloat(num1)?/?parseFloat(num2);
????}
????//設(shè)置結(jié)果輸入框的值?
????document.getElementById("fruit").value?=?result;
???}
??</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(diào)用創(chuàng)建的函數(shù)，得到結(jié)果-->?
???<input?type='text'?id='fruit'/>???
?</body>
</html>