JavaScript, Jquery find index of clicked element
I building slide, and I need am stack at following problem - How can I found position (index) in the array when a tag is clicked? This part of the code is getting all a tag

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

How to go from there?
And also, there is another problem - I need to toggle class of the div inside a tag (when a tag is clicked div tag needs to get class promo_tumb_current and the one which has that tag need to loose 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 code:

    <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();
                        
                        
                    })
</script>

JavaScript, Jquery find index of clicked element
===

I building slide, and I need am stack at following problem - How can I found position (index) in the array when a tag is clicked? This part of the code is getting all a tag

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

How to go from there?
And also, there is another problem - I need to toggle class of the div inside a tag (when a tag is clicked div tag needs to get class promo_tumb_current and the one which has that tag need to loose 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 code:

    <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();
                        
                        
                    })
</script>
