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求問我這個(gè)用if/else寫的為何無法運(yùn)行呢？

<!DOCTYPE?html>
<html>
?<head>
??<title>?事件</title>??
??<script?type="text/javascript">
???function?count(){
?????var?a?=?parseInt(document.getElementById("txt1").value);?
?????var?b?=?parseInt(document.getElementById("txt2").value);????
?????var?c?=?document.getElementById("select").value;
	?var?result?="";
if(c=="+")
{
result=a+b;
}
????else?if(c=="-")
????{
result=a-b;???
????}
????else?if(c=="*")
????{
result=a*b;
????}
????else
????{
result=a/b;
????}
???document.getElementById("fruit").value=result;??
}
????
????//獲取第一個(gè)輸入框的值
	//獲取第二個(gè)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(yùn)算法則
????//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>

qq_帕維爾_0

2015-09-05

源自：JavaScript進(jìn)階篇 6-11

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1 回答

qq_Miss丶不曾忘記_0
2015-09-05

<!DOCTYPE?html>
<html>
?<head>
??<title>?事件</title>??
??<script?type="text/javascript">
???function?count(){
?????var?a?=?parseInt(document.getElementById("txt1").value);?
?????var?b?=?parseInt(document.getElementById("txt2").value);????
?????var?c?=?document.getElementById("select").value;
?????var?result?="";
if(c=="+")
{
result=a+b;
}
????else?if(c=="-")
????{
result=a-b;???
????}
????else?if(c=="*")
????{
result=a*b;
????}
????else
????{
result=a/b;
????}
???document.getElementById("fruit").value=result;??
}//這里多了個(gè)花括號(hào)，去掉就可以了.........................................................................................................
?????
????//獲取第一個(gè)輸入框的值
????//獲取第二個(gè)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(yùn)算法則
????//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()"?/>??
???<input?type='text'?id='fruit'?/>???
?</body>
</html>