為什么我的這個只執(zhí)行最后一個/號啊，中間的直接跳過了
<!DOCTYPE html>
<html>
?<head>
? <title> 事件</title>?
? <script type="text/javascript">
?? function count(){
?????
??? //獲取第一個輸入框的值
?//獲取第二個輸入框的值
?var result;
?//獲取選擇框的值
?var a1=document.getElementById("txt1").value;
?var a2=document.getElementById("txt2").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
??? var fh=document.getElementById("select").value;
??? switch(select){
????? case "+":
???????? result= parseFloat(a1)+parseFloat(a2);
???????? break;
????? case "-":
???????? result=parseFloat(a1)-parseFloat(a2);
???????? break;
????? case "*":
????????? result=parseFloat(a1)*parseFloat(a2);
????????? break;
?????? default:
????????? result=parseFloat(a1)/parseFloat(a2);
?????????
???????
??? }
???
??? //設(shè)置結(jié)果輸入框的值
???
??? document.getElementById("fruit").value=result;
???
?? }
? </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>
2019-04-19
var fh=document.getElementById("select").value;
??? switch(fh){
????? case "+":
???????? result= parseFloat(a1)+parseFloat(a2);
???????? break;
????? case "-":
???????? result=parseFloat(a1)-parseFloat(a2);
???????? break;
????? case "*":
????????? result=parseFloat(a1)*parseFloat(a2);
????????? break;
?????? default:
????????? result=parseFloat(a1)/parseFloat(a2);
??? }