JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.21/themes/pepper-grinder/jquery-ui.css">
<div class="demo"> 
<ol id="selectable">
 <li class="ui-state-default">1</li>
 <li class="ui-state-default">2</li>
 <li class="ui-state-default">3</li>
 <li class="ui-state-default">4</li>
 <li class="ui-state-default">5</li>
 <li class="ui-state-default">6</li>
 <li class="ui-state-default">7</li>
 <li class="ui-state-default">8</li>
 <li class="ui-state-default">9</li>
 <li class="ui-state-default">10</li>
 <li class="ui-state-default">11</li>
 <li class="ui-state-default">12</li>
</ol>
</div>

CSS

#feedback { font-size: 1.4em; }
#selectable .ui-selecting { background: #FECA40; }
#selectable .ui-selected { background: #F39814; color: white; }
#selectable { list-style-type: none; margin: 0; padding: 0; }
#selectable li { margin: 3px; padding: 1px; float: left; width: 100px; height: 80px; font-size: 4em; text-align: center; }

JavaScript

var $currentlySelected = null;
var selected = [];

$('#selectable').selectable({
    start: function(event, ui) {
        $currentlySelected = $('#selectable .ui-selected');
    },
    stop: function(event, ui) {
        for (var i = 0; i < selected.length; i++) {
            if ($.inArray(selected[i], $currentlySelected) >= 0) {
              $(selected[i]).removeClass('ui-selected');
            }
        }
        selected = [];
    },
    selecting: function(event, ui) {
        $currentlySelected.addClass('ui-selected'); // re-apply ui-selected class to currently selected items
    },
    selected: function(event, ui) {
        selected.push(ui.selected); 
    }
});