哪里錯(cuò)了，好難找
<!DOCTYPE html>
<html>
?<head>
? <title> 事件</title> ?
? <script type="text/javascript">
?? function count(){
??? var x=document.getElementById("txt1").value;
??? var x=document.getElementById("txt2").value;
??? var m=document.getElementById("select").value;
??? var sum="";
??? switch(m){
??????? case '+':sum=parseInt(x)+parseInt(y);break;
??????? case '-':sum=parseInt(x)+parseInt(y);break;
??????? case '*':sum=parseInt(x)*parseInt(y);break;
??????? default:sum=parseInt(x)/parseInt(y);break;
??? }
??? document.getElementById("fruit").value=sum;
??? //獲取第一個(gè)輸入框的值
?? ?//獲取第二個(gè)輸入框的值
?? ?//獲取選擇框的值
?? ?//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
??? //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>
2016-06-06
你獲取 兩個(gè)變量都是x,x
???????????? var x=document.getElementById("txt1").value;
???????????? var x=document.getElementById("txt2").value;
后面你用的是 x,y
??????? case '+':sum=parseInt(x)+parseInt(y);break;
??????? case '-':sum=parseInt(x)+parseInt(y);break;
??????? case '*':sum=parseInt(x)*parseInt(y);break;
??????? default:sum=parseInt(x)/parseInt(y);break;