<!DOCTYPE?html>
<html>
?<head>
??<title>?事件</title>??
??<script?type="text/javascript">
???function?count(){
???????
????var?a=?document.getElementById("txt1"）.value;//獲取第一個輸入框的值
var?b=?document.getElementById("txt2"）.value;//獲取第二個輸入框的值
var?c=?document.getElementById("select"）.value;//獲取選擇框的值
var?result="";
????switch(select){
????????case?"+":
????????result=parseFloat(txt1)+parseFloat(txt2);
????????break;
????????case"-";
????????result=parseFloat(txt1)-parseFloat(txt2);
????????break;
????????case"*":
????????result=parseFloat(txt1)*parseFloat(txt2);
????????break;
????????case"/":
????????result=parseFloat(txt1)/parseFloat(txt2);
????}//獲取通過下拉框來選擇的值來改變加減乘除的運算法則
????document.getElementById("fruit"）.value?=result;//設置結果輸入框的值?
????
???}
??</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?=?按鈕來調用創(chuàng)建的函數(shù)，得到結果-->?
???<input?type='text'?id='fruit'?/>???
?</body>
</html>
2015-08-18
?var?a=?document.getElementById("txt1"）.value;//獲取第一個輸入框的值 ?var?b=?document.getElementById("txt2"）.value;//獲取第二個輸入框的值 ?var?c=?document.getElementById("select"）.value;//獲取選擇框的值這3行的）都敲成英文，而且這里定義的變量分別是a,b,c，怎么下面調用時就成txt1,txt2,select。上下改為一致的吧。
var?txt1=?document.getElementById("txt1").value;//獲取第一個輸入框的值 var?txt2=?document.getElementById("txt2").value;//獲取第二個輸入框的值 var?select=?document.getElementById("select").value;//獲取選擇框的值這里的冒號被敲成分號，改成冒號
document.getElementById("fruit"）.value?=result;//設置結果輸入框的值這里的）也被敲成中文的，改成英文的
document.getElementById("fruit").value?=result;//設置結果輸入框的值修改后的全代碼
<!DOCTYPE?html> <html> <head> ????<title>?事件</title> ????<script?type="text/javascript"> ????????function?count(){ ????????????var?txt1=?document.getElementById("txt1").value;//獲取第一個輸入框的值 ????????????var?txt2=?document.getElementById("txt2").value;//獲取第二個輸入框的值 ????????????var?select=?document.getElementById("select").value;//獲取選擇框的值 ????????????var?result=""; ????????????switch(select){ ????????????????case?"+": ????????????????????result=parseFloat(txt1)+parseFloat(txt2); ????????????????????break; ????????????????case"-": ????????????????????result=parseFloat(txt1)-parseFloat(txt2); ????????????????????break; ????????????????case"*": ????????????????????result=parseFloat(txt1)*parseFloat(txt2); ????????????????????break; ????????????????case"/": ????????????????????result=parseFloat(txt1)/parseFloat(txt2); ????????????}//獲取通過下拉框來選擇的值來改變加減乘除的運算法則 ????????????document.getElementById("fruit").value?=result;//設置結果輸入框的值 ????????} ????</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?=?按鈕來調用創(chuàng)建的函數(shù)，得到結果--> <input?type='text'?id='fruit'?/> </body> </html>