<form name='form1' id="form1" method="post">
<table>  
 <tr>
      <td height="10" style="color:#FF0000 " ><span id='radio_id15'>显示器：</span>：</td>
      <td height="10" style="color:#FF0000 ">
        <input type="radio" name="4" value="有"   />有<input type="radio" name="4" value="无"  />无<input type="radio" name="4" value="未知"   />未知</td>
    <td height="10" style="color:#000000 " ><span id='radio_id16'>鼠标</span>：</td>
    <td height="10" style="color:#000000 ">
        <input type="radio" name="7" value="有"   />有<input type="radio" name="7" value="无" />无<input type="radio" name="7" value="未知"   />未知</td></tr>
<tr>
    <td height="10" style="color:#000000 " ><span id='radio_id17'>椅子</span>：</td>
    <td height="10" style="color:#000000 ">
        <input type="radio" name="8" value="有"   />有<input type="radio" name="8" value="无"  />无<input type="radio" name="8" value="未知"   />未知</td>
    <td height="10" style="color:#000000 " ><span id='radio_id18'>电源</span>：</td>
    <td height="10" style="color:#000000 ">
        <input type="radio" name="9" value="有"   />有<input type="radio" name="9" value="无"  />无<input type="radio" name="9" value="未知"   />未知</td></tr>
<tr>
    <td height="10" style="color:#FF0000 "><span id='radio_id19'>网线</span>：</td>
    <td height="10" style="color:#FF0000 ">
        <input type="radio" name="10" value="有"  />有<input type="radio" name="10" value="无"  />无<input type="radio" name="10" value="未知"   />未知</td></tr>
<tr><td height="40" colspan="4"  align="center"><br>
    <input name="save" type="button"  id="btn"  value="下一步"  onclick="sub()" /> 
    <input name="close" type="reset"  value="重新输入"  id="btn"/>
   </td> </tr>
</table>
</form>

function sub() {
        var obj = document.getElementsByTagName("input"); 
        //alert(obj.length);  -->17
        for (var i = 0; i < obj.length; i ++) {
           var id_value = 'radio_id'+ i;
        if (obj[i].type == 'radio' && obj[i].checked ==true && obj[i].value =='有')
        {
            //alert(id_value);
            var aid = document.getElementById("'radio_id'+ i");
            alert(aid.innerHTML);
        }
    }
}