JSFiddle - React, Tailwind, and code Playground

HTML

<b style="float: left; margin-right: 10px;">category 1</b><input type="checkbox" value="category1" style="float: left;" class="portfolio-category" /><br />
<b style="float: left; margin-right: 10px;">category 2</b><input type="checkbox" value="category2" style="float: left;" class="portfolio-category" /><br />
<br />
<br />
<input type="text" name="categories" id="portfolio-categories" />

JavaScript

jQuery(document).ready(function() {
    jQuery(".portfolio-category").click(function() {
        if(jQuery(this).is(":checked")) {
            jQuery("#portfolio-categories").val(jQuery("#portfolio-categories").val()+" "+jQuery(this).val());
        }
        else {
            var portfolioCategories = jQuery("#portfolio-categories").val();    
            alert("before + "+portfolioCategories);
            var currentElement = jQuery(this).val()+" ";
            alert(currentElement);
            portfolioCategories = portfolioCategories.replace(currentElement, "");
            alert(portfolioCategories);
        }
    });
});