                        課程
                    
                        /前端開發
                        
                            /JavaScript
                        
                        /JavaScript進階篇

成功了，最后結果能返回到第三個文本框

<!DOCTYPE html>
<html>
?<head>
? <title> 事件</title> ?
? <script type="text/javascript">
?? function count(){
????? ?
??? var num1,num2,fuhao,jieguo;

??? var fuhao=document.getElementById('select').value;
??? var num1=parseInt(document.getElementById('txt1').value);
??? var num2=parseInt(document.getElementById('txt2').value);
??? switch(fuhao){
??????? case "+" :
??????????? jieguo=num1+num2;
??????????? break;
??????? case "-" :
??????????? jieguo=num1-num2;
??????????? break;
??????? case "*" :
??????????? jieguo=num1*num2;
??????????? break;
??????? case "/" :
??????????? jieguo=num1/num2;
??????????? break;
?? }
??? document.getElementById('fruit').value = jieguo;
??? alert(jieguo);
}
? </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()' /> 
?? <input type='text' id='fruit' value="結果"/>

?</body>
</html>