<!DOCTYPE?html>
<html>
?<head>
??<title>?事件</title>??
??<script?type="text/javascript">
?
???????
????function?count(){
????var?a;
????var?txt1=document.getElementById("txt1").value;
????var?txt2=document.getElementById("txt2").value;
????var?select=document.getElementById("select").value;
????switch(select){
????????case?"+":
????????????a?=?parseFloat(txt1)?+?parseFloat(txt2);
????????break;
????????case?"-":
????????????a?=?parseFloat(txt1)?-?parseFloat(txt2);
????????break;
????????case?"*":
????????????a?=?parseFloat(txt1)?*?parseFloat(txt2);
????????break;
????????case?"/":
????????????a?=?parseFloat(txt1)?/?parseFloat(txt2);
????}
?document.getElementById("fruit").value=a;
???}
????
???
??</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>
2015-03-24
加了的話，如果所有case中的語句都沒有執行的話，則執行default中的執行代碼塊