-- cnblogs checkbox javascrip int ava mage clear img

<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"> 遊泳
<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;
}
}

function clearall(){
var hobby = document.getElementsByName("hobby");
for(var i=0; i<hobby.length;i++ ){
hobby[i].checked=false;
}
}

function checkone(){
var j=document.getElementById("wb").value;
if(parseInt(j)>6||parseInt(j)<1)
{
alert("請輸入1-6之間的數字");
}
var hobby=document.getElementsByName("hobby");
hobby[parseInt(j)-1].checked=true;
}
</script>

(6個name="hobby"的復選項，兩個按鈕)來區分三種方法的不同---區別getElementByID,getElementsByName,getElem