<!DOCTYPE?html>
<html>
?<head>
??<title>?事件</title>??
??<script?type="text/javascript">
???function?count(){
????var?m=document.getElementById("txt1").value;
????var?b=document.getElementById("txt2").value;
????var?c?=document.getElementById("select").value;
//獲取通過下拉框來選擇的值來改變加減乘除的運算法則
????var?result="";
????switch(c){
????????case?'+':
????????????result=parseInt(m)+parseInt(b)?;
????????????break;
????????case?'-':
????????????result=parseInt(m)-parseInt(b);?
????????????break;
????????case?'*':
????????????result=parseInt(m)*parseInt(b)?;
????????????break;
????????default?'/':
????????????result=parseInt(m)/parseInt(b)?;
????????????break;
????}
????
????document.getElementById("fruit")=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?=?按鈕來調用創建的函數，得到結果-->?
???<input?type='text'?id='fruit'?/>???
?</body>
</html>
2015-01-24
簡單來說?document.getElementById("fruit")=result;少個.value
default?'/':
????????????result=parseInt(m)/parseInt(b)?;
????????????break;
default應該改成case
2015-01-24
<!DOCTYPE?html> <html> ?<head> ??<title>?事件</title>?? ??<script?type="text/javascript"> ???function?count(){ ????var?m=document.getElementById("txt1").value; ????var?b=document.getElementById("txt2").value; ????var?c?=document.getElementById("select").value; ????//獲取通過下拉框來選擇的值來改變加減乘除的運算法則 ????var?result="0"; ????switch(c){ ????????case?'+': ????????????alert("+++"); ????????????result=parseInt(m)+parseInt(b)?; ????????????break; ????????case?'-': ????????????result=parseInt(m)-parseInt(b);? ????????????break; ????????case?'*': ????????????result=parseInt(m)*parseInt(b)?; ????????????break; ????????case?'/': ????????????result=parseInt(m)/parseInt(b)?; ????????????break; ????} ?????alert(result); ????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();"/> ???<input?type='text'?id='fruit'?/>??? ?</body> </html>