JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
  <form id="form" method="post" name="">
		<input  type="text" name="email" placeholder="Введите email" value=""/>
		<input type="text" name="phone" placeholder="Введите телефон" value=""  /> <br />
		<input type="submit" name="submit" value="Готово" />
	</form>

CSS

form{
	padding: 20px;
	background-color: #fff;
	max-width: 320px;
	margin: auto;
	position: relative;
}

JavaScript

// Validation function
function valid(form) {
	var isValidMail = form.find('[name=email]').val().length <= 1 ? alert("Вы не ввели email") : true;
	var isValidName = form.find('[name=phone]').val().length <= 1 ? alert("Вы не ввели телефон") : true;  
  return isValidMail && isValidName ? true : false;
}	

// On load
$(document).ready(function() {
	$('#form').on('submit', function () {
  	return valid($(this));
  });
});