脚本实现CheckBox父选中，子全选中，子选中父也选中！

<FORM id=weaver name=frmmain action="DocUserDefaultOperation.jsp" method=post >
<input type="hidden" name="id" value=1>

<table class=Form>
  <tr class=Section>
          <TH colSpan=2>字段</TH>
  </tr>
  <TR class=Separator>
        <TD class=Sep1 colSpan=2></TD>
  </TR>
  <tr class=field>
      <td width="50%">
          <input type="checkbox" name="hascreater" value="1" checked >
          所有者
      </td>
      <td width="50%">
          <input type="checkbox" name="hasdocid" value="1" checked >
          标识
      </td>
  </tr>
  <tr class=field>
      <td width="50%">
          <input type="checkbox" name="hascreatedate" value="1" checked >
          创建日期
      </td>
      <td width="50%">
          <input type="checkbox" name="hascategory" value="1" checked >
          主目录/分目录/子目录
      </td>
  </tr>
  <tr class=field>
      <td width="50%">
          <input type="checkbox" name="hascreatetime" value="1" checked >
          修改日期时间
      </td>
      <td width="50%">
          <input type="checkbox" name="hasreplycount" value="1" checked >
          显示回复总数
      </td>
  </tr>
  <tr class=field>
      <td width="50%">&nbsp;</td>
      <td width="50%">
          <input type="checkbox" name="hasaccessorycount" value="1" checked >
          显示附件总数
      </td>
  </tr>
  <tr class=Section>
          <TH colSpan=2>显示</TH>
  </tr>
  <TR class=Separator>
        <TD class=Sep1 colSpan=2></TD>
  </TR>
  <tr class=field>
      <td>
      每页记录
      <input type="text" class=saveHistory name="numperpage" value=50 size="3" maxlength=2 onKeyPress="ItemCount_KeyPress()" onBlur='checknumber1(this)'>
      条

      </td>
  </tr>
 
  <tr class=Section>
          <TH colSpan=2>主目录 - 目录</TH>
  </tr>
  <TR class=Separator>
        <TD class=Sep1 colSpan=2></TD>
  </TR>
  <tr>
      <td width="50">主目录</td>
      <td width="50%"></td>
  </tr>
  <tr>
      <td width="50%" align="center">分目录</td>
      <td width="50%"></td>
  </tr>
  <tr><td colspan=2></td></tr>
  <TR><TD class=Sep1 colSpan=2></TD></TR>
 
  <tr class=field>
        <td width="50%" align=left valign=top>
       
     <table class=Form>
        <tr class=field>
          <td colspan=2 align=left>
         
          <input type="checkbox" name="m12" value="M12" onclick="checkMain('12')" checked>
         
          <b>系统使用</b> </td></tr>
    
        <tr class="field">
          <td width="20%"></td>
          <td>
         
          <input type="checkbox" name="s12" value="S27" onclick="checkSub('12')" checked>
         
          系统使用规范</td></tr>
   
        <tr class="field">
          <td width="20%"></td>
          <td>
         
          <input type="checkbox" name="s12" value="S28" onclick="checkSub('12')" checked>
         
          系统功能介绍</td></tr>
   
    </table>
   
    
          <table class=Form>
        <tr class=field>
          <td colspan=2 align=left>
         
          <input type="checkbox" name="m7" value="M7" onclick="checkMain('7')" checked>
         
          <b>会议资料</b> </td></tr>
    
        <tr class="field">
          <td width="20%"></td>
          <td>
         
          <input type="checkbox" name="s7" value="S12" onclick="checkSub('7')" checked>
         
          会议资料</td></tr>
   
    </table>
   
        
        </td><td align=left valign=top>
   
  </tr>
</table>
</form>

   
<script>
function checkMain(id) {
len = document.frmmain.elements.length;
var mainchecked=document.all("m"+id).checked ;
var i=0;
for( i=0; i<len; i++) {
if (document.frmmain.elements[i].name=='s'+id) {
document.frmmain.elements[i].checked= mainchecked ;
}
}
}

function checkSub(id) {
len = document.frmmain.elements.length;
var i=0;
for( i=0; i<len; i++) {
if (document.frmmain.elements[i].name=='s'+id) {
    if(document.frmmain.elements[i].checked){
        document.all("m"+id).checked=true;
        return;
        }
    }
}
document.all("m"+id).checked=false;
}

function onSave(){
    if(document.all("numperpage").value != ""&& document.all("numperpage").value*1<=0 ){
        alert("每页记录条数必须大于零");
        return;
    }
    frmmain.submit();
}
</script>