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編程練習(xí)的計(jì)算器代碼，請(qǐng)大家?guī)臀铱纯次业降族e(cuò)哪了？

<!DOCTYPE html>
<html>
?<head>
? <title> 事件</title> ?
? <script type="text/javascript">
?? function count(){
??? var a=document.getElementById('txt1').value;
??? var b=document.getElementById('txt2').value;
?? var? symbol=document.getElementById('select').value;
?? var result='';
?? switch(symbol)
?? {
?????? case'+':
?????? result=parseFloat(a)+parseFloat(b);
?????? break;
?????? case'-'：
?????? result=parseFloat(a)-parseFloat(b);
?????? break;
?????? case'*':
?????????? result=parseFloat(a)*parseFloat(b);
?????????? break;
??????? default:
??????? result=parseFloat(a)/parseFloat(b);
?? }
?? document.getElementById('select').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()? > 
?? <input type='text' id='fruit' />? ?
?</body>
</html>

慕神3775235

2015-09-05

源自：JavaScript進(jìn)階篇 6-11

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3 回答

Perona
2015-09-05

?case'-'：

這里冒號(hào)錯(cuò)了，改成英文冒號(hào)。

document.getElementById('select').value=result;

這里獲取的id名寫錯(cuò)了，也就是說你把值賦給了運(yùn)算符號(hào)的那個(gè)節(jié)點(diǎn)。改成fruit。

修改后的完整代碼

<!DOCTYPE?html>
<html>
<head>
????<title>?事件</title>
????<script?type="text/javascript">
????????function?count(){
????????????var?a=document.getElementById('txt1').value;
????????????var?b=document.getElementById('txt2').value;
????????????var??symbol=document.getElementById('select').value;
????????????var?result='';
????????????switch(symbol)
????????????{
????????????????case'+':
????????????????????result=parseFloat(a)+parseFloat(b);
????????????????????break;
????????????????case'-':
????????????????????result=parseFloat(a)-parseFloat(b);
????????????????????break;
????????????????case'*':
????????????????????result=parseFloat(a)*parseFloat(b);
????????????????????break;
????????????????default:
????????????????????result=parseFloat(a)/parseFloat(b);
????????????}
????????????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>