JSFiddle - React, Tailwind, and code Playground

HTML

<button id="showContent">Показать</button>
<button id="hideContent">Скрыть</button>
<div class="content">Блок 1</div>

<div class="content">Блок 2</div>

<div class="content">Блок 3</div>

JavaScript

var content = document.getElementsByClassName('content'); // возвращает массив элементов

connect.forEach( con=>con.addEventListener("click", () => {
    content.style.display = "block"
}));
let show = document.getElementById("showContent");
let hide = document.getElementById("hideContent");

show.addEventListener("click", () => {
    content.style.display = "block"
})

hide.addEventListener("click", () => {
    content.style.display = "none"
})