js全选实现和判断是否有复选框选中的方法

function actionEvent(methodname){ 
        var form = document.forms[0]; 
        if(validateIsSelect(form.all, form.productids)){ 
            form.action='<html:rewrite action="/control/product/manage"/>'; 
            form.submit(); 
        }else{ 
            alert("请选择要操作的记录"); 
        } 
} 

function allselect(allobj,items){ 
        var state = allobj.checked; 
        if(items.length){ 
            for(var i=0;i<items.length;i++){ 
                if(!items[i].disabled) items[i].checked=state; 
            } 
        }else{ 
            if(!items[i].disabled) items.checked=state; 
        } 
} 
/*
* 判断是否选择了记录
*/ 
function validateIsSelect(allobj,items){ 
        var state = allobj.checked; 
        if(items.length){ 
            for(var i=0;i<items.length;i++){ 
                if(items[i].checked) return true; 
            } 
        }else{ 
            if(items.checked) return true; 
        } 
        return false; 
}

<INPUT TYPE="checkbox" NAME="all"  onclick="javascript:allselect(this, this.form.productids)">全选</td>

<input name="visible" type="button" class="frm_btn" onClick="javascript:actionEvent('visible')" value=" 操作 ">