点击checkbox全选，其它被选中，再点击取消

                                             <input type="checkbox" value="" id="checkall" name="" size="" class="m-wrap  "  onclick="checkfk()">
                                                <span class="">(全选)</span>
                                                <input type="checkbox" name="fkcheck" value="" id="" size="" class="m-wrap  " >
                                                <span class="">现付</span>
                                                <input type="checkbox" name="fkcheck" value="" id="" size="" class="m-wrap  " >
                                                <span class="">到付</span>
                                                <input type="checkbox" name="fkcheck" value="" id="" size="" class="m-wrap  " >
                                                <span class="">月付</span>
                                                <input type="checkbox" name="fkcheck" value="" id="" size="" class="m-wrap  " >
                                                <span class="">回执付</span>
                                                <input type="checkbox" name="fkcheck" value="" id="" size="" class="m-wrap  " >
                                                <span class="">返厂付</span>

function checkfk(){
        var allcheck=document.getElementById("checkall");  //获取 全选check 的id
        var othercheck=document.getElementsByName("fkcheck"); //获取数组名称为fkcheck的 复选框

for(var i=0;i<othercheck.length;i++){ if(allcheck.checked){ othercheck[i].checked=true; }else{ othercheck[i].checked=false; } } }  //循环遍历 复选框 ，当点击全选时，其它被选中，否则取消选中