layui checkbox 反选/全选/取消单个取消全选/全部选中勾上全选

<div class="layui-form-item">
                     <label class="layui-form-label">站点</label>
                     <div class="layui-input-block">
                                <input type="checkbox" lay-skin="primary"  id="c_all" lay-filter="c_all" title="全部">
                                <input type="checkbox" lay-skin="primary"  id="f_all" lay-filter="f_all" title="反选">
                                 <br/><br/>
                                        <input type="checkbox" name="cityId" lay-skin="primary" lay-filter="c_one" class="cityId"  title="北京" value="10001">
                                        <input type="checkbox" name="cityId" lay-skin="primary" lay-filter="c_one" class="cityId"  title="测试" value="10002">
                                        <input type="checkbox" name="cityId" lay-skin="primary" lay-filter="c_one" class="cityId"  title="西安" value="10003">
                                        <input type="checkbox" name="cityId" lay-skin="primary" lay-filter="c_one" class="cityId"  title="常州" value="10004">
                                        <input type="checkbox" name="cityId" lay-skin="primary" lay-filter="c_one" class="cityId"  title="肇庆" value="10005">
           </div>
        </div>
        

  layui.use('form', function () {
        var form = layui.form;
        //全选
        form.on('checkbox(c_all)', function (data) {
            var a = data.elem.checked;
            if (a == true) {
                $(".cityId").prop("checked", true);
                form.render('checkbox');
            } else {
                $(".cityId").prop("checked", false);
                form.render('checkbox');
            }
 
        });
        //反选
        form.on('checkbox(f_all)', function (data) {
            var item = $(".cityId");
            item.each(function () {
                if ($(this).prop("checked")) {
                    $(this).prop("checked", false);
                } else {
                    $(this).prop("checked", true);
                }
            })
            form.render('checkbox');
 
 
        });
        //有一个未选中全选取消选中
        form.on('checkbox(c_one)', function (data) {
            var item = $(".cityId");
            for (var i = 0; i < item.length; i++) {
                if (item[i].checked == false) {
                    $("#c_all").prop("checked", false);
                    form.render('checkbox');
                    break;
                }
            }
            //如果都勾选了  勾上全选
            var  all=item.length;
            for (var i = 0; i < item.length; i++) {
                if (item[i].checked == true) {
                    all--;
                }
            }
            if(all==0){
            $("#c_all").prop("checked", true);
            form.render('checkbox');}
        });
 
 
    });