JSFiddle - React, Tailwind, and code Playground

HTML

<button class='opb'>open blocks</button>
<button class='n1 gen'>generate</button>
<div class='n1 block'></div>
<div class='n1 block'></div>
<div class='n1 block'></div>

CSS

.block {
  width: 100px;
  height: 100px;
  background: black;
  margin: 10px;
  visibility: hidden;
}

.n1 {
  visibility: hidden;
}

JavaScript

var opb = document.querySelector('.opb');
opb.onclick = e => {
  e.target.parentNode.style.display = 'none';
  var n1 = document.querySelector('.n1');
  n1.style.visibility = 'visible';
};
if (localStorage.getItem('an') == 1) opb.click();