JSFiddle - React, Tailwind, and code Playground

HTML

<button>
toggle blur
</button>

CSS

body {
    background-color: #000;
}

body::before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    opacity: 0.4;
    z-index: -1;
    background: url(https://static01.nyt.com/newsgraphics/2017/12/26/2018-1-olympics-climate/assets/images/469466931-1254.jpg) center no-repeat;
    background-size: cover;
    transition: filter 2s;
}

body.blurred::before {
  filter: blur(30px);
}

JavaScript

$('button').on('click',function(){
	$('body').toggleClass('blurred');
})