JSFiddle - React, Tailwind, and code Playground

HTML

<iframe src="http://google.com/" id="foo"></iframe>
<div id="loadingMessage">Loading...</div>

CSS

#loadingMessage {
    width: 100%;
    height: 100%;
    z-index: 1000;
    background: #ccc;
    top: 0px;
    left; 0px;
    position: absolute;
}

JavaScript

$('#foo').ready(function () {
    $('#loadingMessage').css('display', 'none');
});
$('#foo').load(function () {
    $('#loadingMessage').css('display', 'none');
});