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為什么運(yùn)行不出來(lái)

<!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;//獲取通過(guò)下拉框來(lái)選擇的值來(lái)改變加減乘除的運(yùn)算法則
????switch(c)
???????case?"+":
???????????result=parselnt(a)+parselnt(b);
???????????break;
???????case?"-":
???????????result=parselnt(a)-parselnt(b);
???????????break;
???????case?"*":
???????????result=parselnt(a)*parselnt(b);
???????????break;
???????case?"/":
???????????result=parselnt(a)/parselnt(b);
???????????break;
???????????
????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(guò)?=?按鈕來(lái)調(diào)用創(chuàng)建的函數(shù)，得到結(jié)果-->?
???<input?type='text'?id='fruit'?/>???
?</body>
</html>