JSFiddle - React, Tailwind, and code Playground

HTML

<form action="" method="post" id="subnewtopicform" />Title:
<input id="title" type="text" name="title" />
<br/>Description:
<textarea name="description"></textarea>
<br/>Category:
<ul class="list:category categorychecklist form-no-clear" id="categorychecklist">
    <li id="category-19">
        <label class="selectit">
            <input type="radio" id="in-category-19" name="category" value="19">Animation</label>
    </li>
    <li id="category-20">
        <label class="selectit">
            <input type="radio" id="in-category-20" name="category" value="20">Anime</label>
    </li>
</ul>
<input type="submit" value="Submit Topic" class="button-primary" name="subnewtopic" id="subnewtopic" disabled="disabled" />
</form>

JavaScript

jQuery("input[type='text'], textarea").on("keyup", function () {
    if (jQuery(this).val() != "" && jQuery("textarea").val() != "" && jQuery("input[name='category']").is(":checked") == true) {
        jQuery("#subnewtopic").removeAttr("disabled");
    } else {
        jQuery("#subnewtopic").attr("disabled", "disabled");
    }
});

jQuery("input[name='category']").on("change", function () {
    if (jQuery(this).val() != "" && jQuery("textarea").val() != "" && jQuery("input[name='category']").is(":checked") == true) {
        if ($("#title").val() != '')
        {
            jQuery("#subnewtopic").removeAttr("disabled");
        }
    } else {
        jQuery("#subnewtopic").attr("disabled", "disabled");
    }
});