JSFiddle - React, Tailwind, and code Playground

HTML

<button class="trigger">Toggle popup</button>
<div id="layer"></div>
<div class="contact_form"></div>

CSS

body {
    height: 2100px;
    margin:0;
}
html.noscroll {
    position: fixed;
    width: 100%;
    top:0;
    left: 0;
    height: 100%;
    overflow-y: scroll !important;
    z-index: 10;
}
#layer {
    background: #3D464D;
    opacity: 0.6;
    cursor: pointer;
    display: block;
    height: 100%;
    width: 100%;
    position: fixed;
    top:0;
    left: 0;
    z-index: 1;
    display: none;
}
button {
    z-index:4;
    position:fixed;
}
.contact_form {
    width : 60%;
    height : 80%;
    background : rgba(0, 0, 0, 0.7);
    ;
    position : absolute;
    top : 0;
    left : 0;
    right: 0;
    margin: 0 auto;
}

JavaScript

$('button').click(function () {
    $('html').toggleClass('noscroll');
    $('#layer').toggle();
});