javascript触发的select的requierd问题

Question

假设目前有两行select分别为id cat 和 cow，js控制当value时空的option被选择时触发required输出错误信息
js省略大部分

                    <select name="cat1" id="cat1" required>
                        <option value="">ー</option>
                        <option value="1">1</option>
                        <option value="2">2</option>
                        <option value="3">3</option>
                      </select>
                    <select name="cat2" id="cat2" required>
                        <option value="">ー</option>
                        <option value="1">1</option>
                        <option value="2">2</option>
                        <option value="3">3</option>
                      </select>
                    <select name="cow1" id="cow1" required>
                        <option value="">ー</option>
                        <option value="1">1</option>
                        <option value="2">2</option>
                        <option value="3">3</option>
                      </select>
                      <select name="cow2" id="cow2" required>
                        <option value="">ー</option>
                        <option value="1">1</option>
                        <option value="2">2</option>
                        <option value="3">3</option>
                      </select>
                     <div class="errorMsg"></div>
                      <span>一个触发页面跳转页面</span>

<script>
        cat1: function(){
            this.validObj.challenge('cat1', 'cat1') && this.validObj.required();
        },
        cat2: function(){
            this.validObj.challenge('cat2', 'cat2') && this.validObj.required();
        },
        cow1: function(){
            this.validObj.challenge('cow1', 'cow1') && this.validObj.required();
        },
        cow1: function(){
            this.validObj.challenge('cow1', 'cow1') && this.validObj.required();
        },
$.fn.form_check = function(e) {
            var e = e || window.event;
        var page = $.mobile.activePage;
        $('div.inner,input', page).removeClass('error');
        $('p.errorMessage,div.errorBox', page).remove();
        $('span', page).removeClass('admission').removeClass('invalid');
        if (e && $(e.target).closest('a').hasClass('back')) {
            return true;
        }
        var v = new Validator();
        var valid1 = new validationObj({
            validObj: v
        });
        valid1.cat1();
        valid1.cat2();
        valid1.cow1();
        valid1.cow2();
        return !v.has_errors();
    };

这样的话四个select都会在未输入时显示未输入错误信息，请问能否在cat1 cat2第一行的select都被选择非空的option的时候，禁用掉cow的validiton，也即是说即使第二行的cow的select选择value时空的option时也可以跳转，谢谢

Answer 1

       $.fn.form_check = function (e) {
        var e = e || window.event;
        var page = $.mobile.activePage;
        $('div.inner,input', page).removeClass('error');
        $('p.errorMessage,div.errorBox', page).remove();
        $('span', page).removeClass('admission').removeClass('invalid');
        if (e && $(e.target).closest('a').hasClass('back')) {
            return true;
        }
        var v = new Validator();
        var valid1 = new validationObj({
            validObj: v
        });
        valid1.cat1();
        valid1.cat2();
        if (cat1.value != '' && cat2.value != '') {//都不为空再执行验证，同时加上required property
            $('#cow1,#cow2').prop('required',true)
            valid1.cow1();
            valid1.cow2();
        }
        else {//移除required property
            $('#cow1,#cow2').prop('required', false)
        }
        return !v.has_errors();
    };