JSFiddle - React, Tailwind, and code Playground

HTML

<div id="preview_main_block">
			<div class="preview" id="slider_slide1">1</div>
			<div class="preview" id="slider_slide2">2</div>
			<div class="preview" id="slider_slide3">3</div>
</div>

JavaScript

$(function () {
    var $parent = $('#preview_main_block');
    $parent.on('click', '.preview',  function () {
        alert($parent.find('.preview').index($(this)));
    });
});