JSFiddle - React, Tailwind, and code Playground

HTML

<div class="fonForm"></div>
    <div class="divClassForm " id="divWindow">
        <form action="">

            <div class="styleClouse">
                <div class="div_styleClouseOne"></div>
                <div class="div_styleClouseTwo"></div>
            </div>
            <p>Оставить заявку на обратный звонок</p>
            <!-- <span class="close">&times;</span> -->
            <input type="text" placeholder="Ваше имя" class="texName">
            <input type="text" placeholder="Ваш номер телефона" class="textNumbre">
            <input type="submit" value="Отсавиь заявку на звонок" class="btnForm" >
        </form>
    </div>

CSS

.divClassForm {
    display: none;
    position: relative;
    z-index: 9999;
    width: 380px;
    height: 358px;
    position: fixed;
    margin: 0 auto;
    top: 37%;
    left: 40%;
    overflow: auto;
    background: #404040;
    border-radius: 3px;
}

JavaScript

let divClassForm = document.getElementById("divWindow");

console.log(divClassForm);
let block = document.getElementById("idBtnForm");
console.log(block);
let clouse = document.querySelector(".styleClouse");
let fonForm = document.querySelector(".fonForm");

block.onclick = function() {
  divClassForm.style.display = "block";
  fonForm.style.display = "block";
};
clouse.onclick = function() {
  divClassForm.style.display = "none";
  fonForm.style.display = "none";
};