JSFiddle - React, Tailwind, and code Playground

HTML

<button id="resume-button" style="display:none">Resume</button>

JavaScript

var w_focus = true;

window.onblur = function () {
    w_focus = false;
    $('#resume-button').show();
}

$('#resume-button').on('click', function () {
    w_focus = true;
    $('#resume-button').hide();
});