复选框全选或全不选

方法一： <input type="checkbox" name="num2" value="" id="checkedAll" style="display:none;"                                                        onclick="if(this.checked==true) { checkAll1('num2'); } else { clearAll1('num2'); }"  />                         <label for="checkedAll"><input type="button" class="buttonStyle"  value="全选" /></label> <script>function checkAll1(name){    var el = document.getElementsByTagName('input');    var len = el.length;    for(var i=0; i<len; i++)    {        if((el[i].type=="checkbox") && (el[i].name==name)){            el[i].checked = true;}    }}function checkAll2(name){    var el = document.getElementsByTagName('input');    var len = el.length;    for(var i=0; i<len; i++)    {        if((el[i].type=="checkbox") && (el[i].name==name)){            el[i].checked = true;}    }}function clearAll1(name){    var el = document.getElementsByTagName('input');    var len = el.length;    for(var j=0; j<len; j++)    {        if((el[j].type=="checkbox") && (el[j].name==name))        {            el[j].checked = false;        }    }}function clearAll2(name){    var el = document.getElementsByTagName('input');    var len = el.length;    for(var j=0; j<len; j++)    {        if((el[j].type=="checkbox") && (el[j].name==name))        {            el[j].checked = false;        }    }}</script>