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js編程練習題實現簡單計算功能答案

<!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 txt1=document.getElementById("txt1").value;
??? document.write(txt1);
?? ?//獲取第二個輸入框的值
??? var txt2=document.getElementById("txt2").value;
??? document.write(txt2);
?? ?//獲取選擇框的值
??? var select=document.getElementById("select").value;
??? document.write(select);
?? ?//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 result;
??? switch(select){
??????? case "+":
??????????? result=parseInt(txt1)+parseInt{txt2);
??????????? break;
??????? case "-":
??????????? result=parseInt(txt1)-parseInt{txt2);
??????????? break;?????? ?
??????? case "*":
??????????? result=parseInt(txt1)*parseInt{txt2);
??????????? break;?????? ?
??????? case "/":
??????????? result=parseInt(txt1)/parseInt{txt2);
??? }
??? //設置結果輸入框的值
??? var fruit=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()"/> 
?? <input type='text' id='fruit'/>? ?
?</body>
</html>