<!DOCTYPE?html>
<html>
?<head>
??<title>?事件</title>??
??<script?type="text/javascript">
???function?count(){
???????
????var?a=parseInt(document.getElementById("txt1").value);
????//獲取第一個輸入框的值
????var?b=parseInt(document.getElementById("txt2").value);
//獲取第二個輸入框的值
var?c=document.getElementById("select").value;
//獲取選擇框的值
var?sum="";
switch(c)
{
????case?'+':
????????sum=a+b;
????case?'-':
????????sum=a-b;
????case?'*':
????????sum=a*b;
????case?'/':
????????sum=a/b;
???default:
????????sum=0;
}
document.getElementById("fruit").value=sum;
//獲取通過下拉框來選擇的值來改變加減乘除的運算法則
????//設置結果輸入框的值?
????
???}
??</script>?
?</head>?
?<body>
???<input?type='text'?id='txt1'?/>?
???<br>
???<select?id='select'>
<option?value='+'>+</option>
<option?value="-">-</option>
<option?value="*">*</option>
<option?value="/">/</option>
???</select>
???<br>
???<input?type='text'?id='txt2'?/>?
???<br>
???<input?type='button'?value='?=?'?onclick="count()"?/>?<!--通過?=?按鈕來調用創建的函數，得到結果-->
???<br>
???<input?type='text'?id='fruit'?/>???
?</body>
</html>
2017-02-15
沒有break，它會向下執行
2017-02-15
沒有用break跳出循環，一直會執行到最后default