JavaScript and Jquery: Find the index of the clicked element

Question

I'm building a slideshow and I'm having difficulty with the following question - How do I find the position (index) in an array when a label is clicked? The following code section obtains all a tags

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

Where to start? One more problem - when the label is clicked, I need to switch the class of the div inside the label (the div label needs to get class promo_tumb_current, and the div with that label needs to lose it).

HTML code:

<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();


                })

Answer 1

I think what you need is

http://api.jquery.com/index/

For example, in your event handler (where this is the clicked a tag):

var index = thumbs.index($(this))