<script type="text/javascript">
function checkall(){
var hobby = document.getElementsByTagName("input");
// 任务1
for(var i=0;i<hobby.length;i++){
if (hobby[i].type=="checkbox"){
hobby[i].checked=true;
}
}
}
function clearall(){
var hobby = document.getElementsByName("hobby");
// 任务2
for(var i=0;i<hobby.length;i++){
hobby[i].checked=false;
}
}
function checkone(){
var j=document.getElementById("wb").value;
// 任务3
document.getElementById("hobby"+j).checked=true;
}
</script>
<!DOCTYPE HTML><html> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312"> <title>无标题文档</title> </head> <body> <form> 请选择你爱好:<br> <input type="checkbox" name="hobby" id="hobby1"> 音乐 <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"> 阅读 <input type="checkbox" name="hobby" id="hobby5"> 打球 <input type="checkbox" name="hobby" id="hobby6"> 跑步 <br> <input type="button" value = "全选" onclick = "checkall();"> <input type="button" value = "全不选" onclick = "clearall();"> <p>请输入您要选择爱好的序号，序号为1-6:</p> <input id="wb" name="wb" type="text" > <input name="ok" type="button" value="确定" onclick = "checkone();"> </form> <script type="text/javascript"> function checkall(){ var hobby = document.getElementsByTagName("input"); if(hobby.type == 'checkbox'){ for(var i = 0; i<hobby.length; i++){ hobby[i].checked = 'true' } } // 任务1 } function clearall(){ var hobby = document.getElementsByTagName("input"); if(hobby.type == 'checkbox'){ for(var i = 0; i<hobby.length; i++){ hobby[i].checked = '' } } // 任务2 } function checkone(){ var j=document.getElementById("wb").value; var i = j - 1; var hobby = document.getElementsByTagName("input"); if(hobby.type == 'checkbox'){ hobby[i].checked = 'true'; } if(j !== ''){ document.getElementById("wb").value = ''; } // 任务3 } </script> </body></html>最后的"hobby"+j是什么意思