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幫我看看錯(cuò)在哪里？為什么出不來結(jié)果？

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

Bill0123

2015-08-18

源自：JavaScript進(jìn)階篇 6-11

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1 回答

Perona
2015-08-18

?var?a=?document.getElementById("txt1"）.value;//獲取第一個(gè)輸入框的值
?var?b=?document.getElementById("txt2"）.value;//獲取第二個(gè)輸入框的值
?var?c=?document.getElementById("select"）.value;//獲取選擇框的值

這3行的）都敲成英文，而且這里定義的變量分別是a,b,c，怎么下面調(diào)用時(shí)就成txt1,txt2,select。上下改為一致的吧。

var?txt1=?document.getElementById("txt1").value;//獲取第一個(gè)輸入框的值
var?txt2=?document.getElementById("txt2").value;//獲取第二個(gè)輸入框的值
var?select=?document.getElementById("select").value;//獲取選擇框的值

case"-";

這里的冒號(hào)被敲成分號(hào)，改成冒號(hào)

case"-":

document.getElementById("fruit"）.value?=result;//設(shè)置結(jié)果輸入框的值

這里的）也被敲成中文的，改成英文的

document.getElementById("fruit").value?=result;//設(shè)置結(jié)果輸入框的值

修改后的全代碼

<!DOCTYPE?html>
<html>
<head>
????<title>?事件</title>
????<script?type="text/javascript">
????????function?count(){

????????????var?txt1=?document.getElementById("txt1").value;//獲取第一個(gè)輸入框的值
????????????var?txt2=?document.getElementById("txt2").value;//獲取第二個(gè)輸入框的值
????????????var?select=?document.getElementById("select").value;//獲取選擇框的值
????????????var?result="";
????????????switch(select){
????????????????case?"+":
????????????????????result=parseFloat(txt1)+parseFloat(txt2);
????????????????????break;
????????????????case"-":
????????????????????result=parseFloat(txt1)-parseFloat(txt2);
????????????????????break;
????????????????case"*":
????????????????????result=parseFloat(txt1)*parseFloat(txt2);
????????????????????break;
????????????????case"/":
????????????????????result=parseFloat(txt1)/parseFloat(txt2);
????????????}//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
????????????document.getElementById("fruit").value?=result;//設(shè)置結(jié)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(diào)用創(chuàng)建的函數(shù)，得到結(jié)果-->
<input?type='text'?id='fruit'?/>
</body>
</html>