我的為什么運行不出來結(jié)果呢
<!DOCTYPE html>
<html>
?<head>
? <title> 事件</title>?
? <script type="text/javascript">
?? function count(){
??????
??? //獲取第一個輸入框的值
??? var a=parseInt(document.getElementById("txt1").value);
?//獲取第二個輸入框的值
?var b=parseInt(document.getElementById("txt2").value);
?//獲取選擇框的值
?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
??? //設(shè)置結(jié)果輸入框的值
??? var sum;
???
??? switch(c){
??????? case "+"
??????????? sum=a+b;
?????
??????? case "-"
??????????? sum=a-b;
???????????
??????
??????? case "*"
??????????? sum=a*b;
?????
??????? case "/"
??????????? sum=a/b;
??????? break;
??? }
??? document.getElementById("fruit").value=sum;
?? }
???
? </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>
2020-01-20
switch case那一段代碼改改，首先case后面要加冒號，然后每一次判斷后都要加break，代碼如下：
switch?(c)?{???????????? ????case?"+":???????????? ????sum?=?a?+?b;???????????? ????break;???????????? ????case?"-":???????????? ????sum?=?a?-?b;???????????? ????break;???????????? ????case?"*":???????????? ????sum?=?a?*?b;???????????? ????break;???????????? ????case?"/":???????????? ????sum?=?a?/?b;???????????? ????break;???????? }