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                        /JavaScript進(jìn)階篇

計(jì)算器不能得出結(jié)果

<!DOCTYPE?html>
<html>
?<head>
??<title>?事件</title>??
??<script?type="text/javascript">
???function?count(){
???????
????//獲取第一個(gè)輸入框的值
????var?a=document.getElementById("txt1").value;
	//獲取第二個(gè)輸入框的值
????var?b=document.getElementById("txt2").value;
	//獲取選擇框的值
????var?c=document.getElementById("select").value;
????
????var?result="";
????
	//獲取通過下拉框來選擇的值來改變加減乘除的運(yùn)算法則
????switch?select(c){
????????case?"+":
????????????result=parseFloat(a)+parseFloat(b);
????????????break;
????????case?"-":
????????????result=parseFloat(a)+parseFloat(b);
????????????break;
????????case?"*":
????????????result=parseFloat(a)*parseFloat(b);
????????????break;
????????case?"/":
????????????result=parseFloat(a)/parseFloat(b);
????????????break;
????????default:
????????????alert("見鬼！");
????????????break;
????}
????//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>