求助?。。?！
<!DOCTYPE HTML>
<html>
?? ?<head>
?? ??? ?<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
?? ??? ?<title>無標(biāo)題文檔</title>
?? ?</head>
?? ?<body>
?? ??? ?<form>
?? ??? ??? ?請選擇你愛好:<br>
?? ??? ??? ?<input type="checkbox" name="hobby" id="hobby1"> 音樂
?? ??? ??? ?<input type="checkbox" name="hobby" id="hobby2"> 登山
?? ??? ??? ?<input type="checkbox" name="hobby" id="hobby3"> 游泳
?? ??? ??? ?<input type="checkbox" name="hobby" id="hobby4"> 閱讀
?? ??? ??? ?<input type="checkbox" name="hobby" id="hobby5"> 打球
?? ??? ??? ?<input type="checkbox" name="hobby" id="hobby6"> 跑步 <br>
?? ??? ??? ?<input type="button" value="全選" onclick="checkall();">
?? ??? ??? ?<input type="button" value="全不選" onclick="clearall();">
?? ??? ??? ?<p>請輸入您要選擇愛好的序號，序號為1-6:</p>
?? ??? ??? ?<input id="wb" name="wb" type="text">
?? ??? ??? ?<input name="ok" type="button" value="確定" onclick="checkone();">
?? ??? ?</form>
?? ??? ?<script type="text/javascript">
?? ??? ??? ?function checkall() {
?? ??? ??? ??? ?var hobby = document.getElementsByTagName("input");
?? ??? ??? ??? ?for(var i = 0; i < hobby.length; i++) {
?? ??? ??? ??? ??? ?hobby[i].checked = true;
?? ??? ??? ??? ?}
?? ??? ??? ??? ?// 任務(wù)1
?? ??? ??? ?}
?? ??? ??? ?function clearall() {
?? ??? ??? ??? ?var hobby = document.getElementsByName("hobby");
?? ??? ??? ??? ?for(var i = 0; i < hobby.length; i++) {
?? ??? ??? ??? ??? ?hobby[i].checked = false;
?? ??? ??? ??? ?}
?? ??? ??? ??? ?// 任務(wù)2?? ?
?? ??? ??? ?}
?? ??? ??? ?function checkone() {
?? ??? ??? ??? ?var hobby = document.getElementsByName("hobby");
?? ??? ??? ??? ?var j = document.getElementById("wb").value;
?? ??? ??? ??? ?for(var j = 0; j < hobby.length; j++) {
?? ??? ??? ??? ??? ?hobby[j - 1].checked = true;
?? ??? ??? ??? ?}
?? ??? ??? ??? ?// 任務(wù)3
?? ??? ??? ?}
?? ??? ?</script>
?? ?</body>
</html>
實現(xiàn)第三個功能的代碼。如何更改。 同學(xué)代碼理解不了。 謝謝
2017-07-12
額，走了 99，就是最后一步錯了
修改代碼如下：
function checkone() {
????var hobby = document.getElementsByName("hobby");
????var j = document.getElementById("wb").value;
????hobby[j-1].checked = true;
}
注意細(xì)心，謝謝采納