JSFiddle - React, Tailwind, and code Playground

HTML

<div id="campaignTags">
    <div class="tags">Tag 1</div>
    <div class="tags">Tag 2</div>
    <div class="tags">Tag 3</div>
</div>
<label>Enter a tag: <input id="tag" /></label>

JavaScript

var $container = $('#campaignTags'),
    $template  = $('<div class="tags">');

$('#tag').keyup(function(e) {
    if (e.which === 13) {
        var tag = this.value,
            $taggedChild = $('#campaignTags').children().filter(function() {
                return $(this).text() === tag;
            });
        if (! $taggedChild.length) {
            $template.clone().text(tag).appendTo($container);
        }
    }
});