区别getElementByID,getElementsByName,getElementsByTagName@慕课网原创_慕课网

<!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");
        for(var i=0;i<hobby.length;i++){
            hobby[i].checked=true;

        }
      // 任务1 
    }
    function clearall(){
        var hobby = document.getElementsByName("hobby");
        //alert(hobby.length);
        for(var i=0;i<hobby.length;i++){
            hobby[i].checked=false;
        }
     // 任务2  
    }

    function checkone(){
        clearall();
        var hobby = document.getElementsByName("hobby6");
        var j=document.getElementById("wb").value;
        for(var i=0;i<j.length;i++){
            if(j.charAt(i)>6 || j.charAt(i)<1){
                alert("越界,请重新输入！");
                document.getElementById("wb").value="";
            }
        }
            for(var n=0;n<j.length;n++){

                    hobby[(j.charAt(n))-1].checked=true; 
            }

    }

    </script>
</body>

</html>