<!DOCTYPE?html>
<html>
?<head>
??<title>?事件</title>??
??<script?type="text/javascript">
???function?count(){
???????var?one,two,sel,fruit,res;???????
????//獲取第一個輸入框的值
????one?=?parseInt(document.getElementById("txt1").value);
????//獲取第二個輸入框的值
????two?=?parseInt(document.getElementById('txt2').value);
//獲取選擇框的值
????sel?=?document.getElementById("select").value;
????fruit?=?document.getElementById("fruit").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
????switch(sel){
????????case?'+':
????????????res?=?one+two;
????????????break;
????????case?'-':
????????????res?=?one-two;
????????????break;
????????case?'*':
????????????res?=?one*two;
????????????break;
????????case?'/':
????????????res?=?one/two;
????}
????
????
????//設(shè)置結(jié)果輸入框的值?
????fruit?=?res;
<!--?document.getElementById('fruit').value?=?res;?-->
???}
??</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>
2014-11-08
看不懂。。
?fruit?=?res;→你把值給一個變量干嘛？fruit只是一個變量而已，不會對應(yīng)到dom里
????<!--?document.getElementById('fruit').value?=?res;?-->→這里才操作DOM來改變文本框的值，之前寫的才是對的。