jQuery判断checkbox是否选中以及赋值

/判断是否选中：
if ($("#customControlValidationSuccess4").is(':checked'))

//赋值，设置checkbox选中或不选中：
$("#customControlValidationSuccess4").attr("checked", true);


//一个例子：点击checkbox后切换flag状态
<input type="checkbox" id="customControlValidationSuccess4" flag>     

 var flag = false;
 var that = this;
 $('#customControlValidationSuccess4').on('click', function () {
            if ($(this).is(':checked')) {   
                that.flag = true;   
            } else {  
                that.flag = false;
            }
        })