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求大神告訴我這個為何不能計算

<!DOCTYPE?html>
<html>
?<head>
??<title>?事件</title>??
??<script?type="text/javascript">
???function?count(){
????var?num1=document.getElementById("txt1"?).value;
????var?num2=document.getElementById("txt2"?).value;
????var?num3=document.getElementById("select"?).value;
????var?console="";
????switch(num3){
????????case?"+":console=parseInt(num1)+parseInt(num2)?break;
????????case?"-":console=parseInt(num1)-parseInt(num2)?break;
????????case?"*":console=parseInt(num1)*parseInt(num2)?break;
????????default:console=parseInt(num1)+parseInt(num2);
????}
????document.getElementById("fruit").value=console;
????//獲取第一個輸入框的值
????//獲取第二個輸入框的值
????//獲取選擇框的值
????//獲取通過下拉框來選擇的值來改變加減乘除的運算法則
????//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?=?按鈕來調用創建的函數，得到結果-->?
???<input?type='text'?id='fruit'?/>???
?</body>
</html>

qq_大橙子_4

2015-12-01

源自：JavaScript進階篇 6-11

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一毛錢回答被采納 +3 積分
2015-12-01

<!DOCTYPE?html>
<html>

<head>
????<title>?事件</title>
????<script?type="text/javascript">
????function?count()?{
????????var?num1?=?document.getElementById("txt1").value;
????????var?num2?=?document.getElementById("txt2").value;
????????var?num3?=?document.getElementById("select").value;
????????var?console?=?"";
????????switch?(num3)?{
????????????case?"+":
????????????//這塊缺少了分號，下同
????????????????console?=?parseInt(num1)?+?parseInt(num2);
?????????????????break;
????????????case?"-":
????????????????console?=?parseInt(num1)?-?parseInt(num2);
?????????????????break;
????????????case?"*":
????????????????console?=?parseInt(num1)?*?parseInt(num2);
?????????????????break;
????????????default:
????????????????console?=?parseInt(num1)?+?parseInt(num2);
????????????????//這塊缺少了break
????????????????break;
????????}
????????document.getElementById("fruit").value?=?console;
????????//獲取第一個輸入框的值
????????//獲取第二個輸入框的值
????????//獲取選擇框的值
????????//獲取通過下拉框來選擇的值來改變加減乘除的運算法則
????????//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?=?按鈕來調用創建的函數，得到結果-->
????<input?type='text'?id='fruit'?/>
</body>

</html>

問題標注出來了，修改后的代碼如上