JSFiddle - React, Tailwind, and code Playground

JavaScript

var divCount = 1;
var collageCount = 1;

function makeDiv(){
      var divsize = ((Math.random()*100) + 50).toFixed();
    var color = '#'+ Math.round(0xffffff * Math.random()).toString(16);
    $newdiv = $('<div class="collage popup-' + divCount + '"/>').css({
        'width':divsize+'px',
        'height':divsize+'px',
        'background-color': color
    });
    
    var posx = (Math.random() * ($(document).width() - divsize)).toFixed();
    var posy = (Math.random() * ($(document).height() - divsize)).toFixed();
    
    $newdiv.css({
        'position':'absolute',
        'left':posx+'px',
        'top':posy+'px',
        'display':'none'
    }).appendTo( 'body' ).fadeIn(5000, function(){ 
       makeDiv(); 
    });
    divCount++;
}



makeDiv();

function removeDiv(){ 
	$(".popup-" + collageCount + "").fadeOut(300, function() { $(this).remove(); });
  collageCount++;
};

setInterval(function () {
  removeDiv(); // show next div
}, 10 * 1000);