JSFiddle - React, Tailwind, and code Playground

HTML

<div class='main'>
<p>Bacon ipsum dolor sit amet pork chop kielbasa tri-tip bacon turkey.  Pig filet mignon bresaola, shankle tongue salami chuck swine.  Ham hock brisket leberkas, meatloaf rump tenderloin kielbasa bacon shank beef ribs pork loin.  Leberkas tongue venison boudin strip steak.  Ribeye pastrami meatball, short ribs drumstick strip steak pig turkey brisket short loin.  Boudin filet mignon pork, flank meatloaf shank pastrami tri-tip.</p><p>Ground round meatball tongue, short ribs salami turducken bacon.  Ham pork belly sirloin, prosciutto tongue pig fatback beef ribs ball tip chuck brisket jowl.  Bresaola pork prosciutto, short loin ham beef ribs tenderloin fatback.  Tenderloin sirloin spare ribs corned beef.  Tongue prosciutto pancetta sausage bresaola, boudin strip steak meatloaf ball tip turducken.  Swine spare ribs flank ham, sirloin pork belly turkey chuck pork jerky tongue leberkas bacon.  Andouille beef tri-tip biltong ham hock brisket, salami spare ribs short ribs pancetta.</p>

<button id='btn'>Modal</button>


<p>Pastrami swine tri-tip prosciutto, pig pork loin pork shank.  Pork belly tail t-bone pork, pancetta short ribs tri-tip drumstick turkey flank corned beef pork chop sirloin.  Meatloaf filet mignon venison, short loin boudin cow rump tongue shankle kielbasa ball tip jerky tenderloin brisket t-bone.  Frankfurter pancetta brisket, chicken capicola cow chuck ground round beef ball tip biltong swine.</p><p>Pancetta tongue capicola ham, corned beef pastrami chuck salami ribeye t-bone tri-tip shoulder swine hamburger tenderloin.  Chuck fatback meatball pork loin drumstick cow.  Beef ribs biltong shank chicken tongue pork pastrami swine pig, ground round shoulder cow sausage meatball pork loin.  Tail meatloaf spare ribs, flank jerky bacon ham hock venison kielbasa short ribs.  Sausage capicola pig boudin pork tail chuck ribeye, meatball turducken pastrami brisket turkey swine shoulder.  Shank short loin short ribs pig ribeye swine,...

CSS

.modal {
    position: fixed;
    top: 0; left: 0; bottom: 0; right: 0;
    opacity: .9;
    overflow: auto;
    
    color: #fff;
    background: #000;
}

.hidden {
    display: none;
}

JavaScript

$('btn').addEvent('click', toggleModal);
$$('.modal')
    .addEvent('click', toggleModal)
    .adopt($$('.main')[0].clone().getChildren())
    ;

//setInterval(toggleModal, 1000);
    
var toggle = true;
function toggleModal() {
    toggle = !toggle;
    var body = $$('body')[0];
    var html = $$('html')[0];
    var modal = $$('.modal')[0];
    if (toggle) {
        html.setStyles({
            'overflow': 'auto'
            ,'padding-right': '0px'
        });
        
        modal.addClass('hidden');
    } else {
        
        html.setStyles({
            'overflow': 'hidden'
            ,'padding-right': '16px'
        });
        
        modal.removeClass('hidden');
        
    }
}