开发一个谷歌扩展，怎么获取当前页面代码中ul标签下li标签下a标签下span标签的值，span标签有俩个并且值不固定

        <ul data-property="颜色分类" class="J_TSaleProp tb-img tb-clearfix">
            
                    <li data-value="1627207:14186027082" >
                        <a href="javascript:;" style="background:url(//gd1.alicdn.com/imgextra/i1/1683510346/O1CN01c0SB1Z1EQVjdzXlBI_!!1683510346.png_30x30.jpg) center no-repeat;">
                            <span>White/Silver/Nightlife</span>
                        </a>
                        <i>已选中</i>
                    </li>
                
            
                    <li data-value="1627207:13747017907" >
                        <a href="javascript:;" style="background:url(//gd4.alicdn.com/imgextra/i4/1683510346/O1CN01MAHIpK1EQVjd58f4Q_!!1683510346.png_30x30.jpg) center no-repeat;">
                            <span>Nightlife/White/Black</span>
                        </a>
                        <i>已选中</i>
                    </li>
                
            
        </ul>