JSFiddle - React, Tailwind, and code Playground

HTML

<form id="form_a">
    <label>First Name</name><input type="text" class="required"><br>
    <label>Email</label><input type="text" class="required">
<button >Submit</button>
</form>

<form id="form_b">
    <label>Serial No </name><input type="text" class="required"><br>
    <label>Brand </label><input type="text" class="required">
<button >Submit</button>
</form>

<form id="form_c">
    <label>First Name</name><input type="text" class="required"><br>
    <label>Email</label><input type="text" class="required">
<button>Submit</button>
</form>

JavaScript

$(document).ready(function(){
    $("button").click(function(e){
        e.preventDefault();
        $(this).parent().children('.required').each(function(){
            if ($(this).val().indexOf() < 0){
                alert("null value detected");
                $(this).css("border","1px solid red");
            }
        });
    });
});