js 检查内容是否为空

  var NoViods = document.getElementsByClassName("NoVoid");
            for (var i = 0; i < NoViods.length; i++) {
                if (NoViods[i].value.trim() == "") {
                    console.log($('#form1').serialize());
                    alert(NoViods[i].placeholder +" 内容不能空");
                    return false;
                }
            }