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                        /前端開發
                        
                            /JavaScript
                        
                        /JavaScript進階篇

供大家參考

<!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?num1?=?document.getElementById("txt1").value;
??????//獲取第二個輸入框的值	
??????var?num2?=?document.getElementById("txt2").value;	
??????//獲取選擇框的值	
??????var?choice?=?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	
??????var?result;	
??????switch(choice){	???
???????case?'+'?:?result?=?parseInt(num1)+parseInt(num2);?break;?
???????/*parseInt()函數可解析一個字符串,并返回一個整數*/	????
???????case?'-'?:?result?=?num1-num2;?break;	?
???????case?'*'?:?result?=?num1*num2;?break;	??
???????default:???result?=?num1/num2;?break;	}??
?????????//設置結果輸入框的值??
???????document.getElementById("fruit").value?=?result;???}?
????????</script>??</head>??<body>?
??????????<input?type='text'?id='txt1'?/>??
????????????<select?id='select'?onclick="count()">
????????????????	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?=?按鈕來調用創建的函數，得到結果-->??
????????????????	?<input?type='text'?id='fruit'?/>??
????????????????		??????</body></html>