<button class="btn btn_big" type="button" onClick="chkall(0)" >反选</button>
<button class="btn btn_big" type="button" onClick="chkall(1)" >全选</button>
<button class="btn btn_big" type="button" onClick="chkall(2)" >全不选</button>

function chkall(v){
        var ck=document.getElementsByName("xuanze_fz");//定义checkbox数组变量
        for(var i=0;i<ck.length;i++){
            if (!ck[i].disabled){//被禁用的不执行操作选择，跳过
                if (v==0){
                    ck[i].checked=!ck[i].checked;
                }else if (v==1){
                    ck[i].checked='checked';
                }else if (v==2){
                    ck[i].checked='';
                }
            }
        }
    }