JSFiddle - React, Tailwind, and code Playground

HTML

<p>текст станет размытым</p>

CSS

body{
    background: url(http://brightwallpapers.ru/Uploads/7-5-2014/50017/thumb2-mozaika-abstrakcija-treygolniki.jpg);
}

.active{
    -webkit-filter: blur(1px);
}

JavaScript

function hold(e, f, t){
   var holder;
   e.addEventListener("mousedown", function(r){
         holder = setTimeout(function(){
               f.call(e, r);
         }, t || 2000)
   });
   e.addEventListener("mouseup", function(){
        holder && clearTimeout(holder);
   });
}

hold(document.body, function(){
    this.classList.add("active");
}, 3000);