js非空判断有关问题100分

<div class="answer">
                    <ul id="ul1">
                        <span>答案：</span>
                        <input name="radio" type="radio" value="" id="1" onclick="radio_click('ul1',1)"
                            class="nav_1" />
                        <label class="btn_1" value="" onclick="lable_click('ul1',1,1)">
                        </label>
                        <input name="radio" type="radio" value="" id="2" onclick="radio_click('ul1',2)"
                            class="nav_1" />
                        <label class="btn_2" value="" onclick="lable_click('ul1',2,2)">
                        </label>
                        <input name="radio" type="radio" value="" id="3" onclick="radio_click('ul1',3)"
                            class="nav_1" />
                        <label class="btn_3" value="" onclick="lable_click('ul1',3,3)">
                        </label>
                        <input name="radio" type="radio" value="" id="4" onclick="radio_click('ul1',4)"
                            class="nav_1" />
                        <label class="btn_4" value="" onclick="lable_click('ul1',4,4)">
                        </label>
                    </ul>
                </div>