JSFiddle - React, Tailwind, and code Playground

HTML

<button>
    SIMULATE ADDING FORM
</button>
<br>
<br>

CSS

form {
    padding: 10px;
    border: 1px solid red;
    margin-bottom: 20px;
}

h1 {
    margin: 0;
    padding: 0;
}

JavaScript

$(document).ready(function() {

    var keywords = "this is a test keyword";
    var formCount = $("form").length;

    var observer = new MutationObserver(function() {
        var newFormCount = $("form").length;
        if (newFormCount > formCount) {
            $('input[name=netres-keywords]').last().val(keywords);
        }
    });

    $("button").click(function() {
        $form = $("<form>").html("<h1>New form:</h1><input type='text' name='netres-keywords'>");
        $("body").append($form);
    });
    
    var observerConfig = {
	    attributes: true, 
	    childList: true, 
	    characterData: true 
    };
    
    var targetNode = document.body;
    observer.observe(targetNode, observerConfig);
});