我正在构建一个幻灯片，我在以下问题上遇到了困难 - 当点击标签时，如何在数组中找到位置（索引）？下面的代码部分获取了所有的a标签

this.thumbs = this.nav.find('a');

从那里开始呢？ 还有一个问题 - 当点击标签时，我需要切换标签内部div的类（div标签需要获取class promo_tumb_current，而具有该标签的div需要失去它）。

HTML代码：

<div class="promo_tumbs col_12">
    <div data-dir="prev" class="prev"></div>
    <div data-dir="next" class="next"></div>
    <div class="promo_tumbs_centar">
        <a href="#first"><div class="promo_tumb promo_tumb_current"></div></a>
        <a href="#second"><div class="promo_tumb"></div></a>
        <a href="#thrid"><div class="promo_tumb"></div></a>
        <a href="#fourh"><div class="promo_tumb"></div></a>
        <a href="#fifth"><div class="promo_tumb"></div></a>
        <a href="#fifth"><div class="promo_tumb"></div></a>
        <a href="#fifth"><div class="promo_tumb"></div></a>
    </div>
</div>

JS代码：

<script>
                function Slider(container, nav){
                    this.container = container;
                    this.nav = nav;

                    this.li = this.container.find('li');
                    this.li_width = this.li.first().width();
                    this.li_len = this.li.length;

                    this.thumbs = this.nav.find('a');

                    this.current = 0;
                }

                Slider.prototype.transition = function (coords){
                    this.container.stop().animate({
                        'margin-left' : coords || -(this.current * this.li_width)
                    })
                }

                Slider.prototype.set_current = function(dir){
                    var pos = this.current;
                    if (dir === 'next') {pos++}
                    else if (dir === 'prev') {pos--}                
                    this.current = (pos < 0) ? this.li_len - 1 : pos % this.li_len;

                    return pos;
                }

                var slider = new Slider($('div.promo_inner ul'), $('div.promo_tumbs'));
                    slider.nav.find('div').on('click', function(){                               
                    if ($(this).attr("data-dir") === undefined ) {
                        var index = slider.thumbs.index();

                        console.log(index)
                    } else {
                         slider.set_current($(this).data('dir'));                    
                    }               
                    slider.transition();


                })