JSFiddle - React, Tailwind, and code Playground

HTML

<div class="group">
	  <p class="name">Первый</p>
	  <div class="blocks">
	    <div class="block">1</div>
	    <div class="block">2</div>
	    <div class="block">3</div>
	    <div class="block">4</div>
	  </div>
	  <div class="enter">Добавить</div>
	</div>
	<div class="group">
	  <p class="name">Второй</p>
	  <div class="blocks">
	    <div class="block">1</div>
	    <div class="block">2</div>
	    <div class="block">3</div>
	    <div class="block">4</div>
	  </div>
	  <div class="enter">Добавить</div>
	</div>
	<div class="group">
	  <p class="name">Третий</p>
	  <div class="blocks">
	    <div class="block">1</div>
	    <div class="block">2</div>
	    <div class="block">3</div>
	    <div class="block">4</div>
	  </div>
	  <div class="enter">Добавить</div>
	</div>

CSS

.group {
	  background: #cccccc;
	  margin: 20px;
	  width: min-content;
	  text-align: center;
	  display: flex;
	  flex-wrap: wrap;
	  justify-content: center;
	}

	.blocks {
	  display: flex;
	}

	p {
	  flex-basis: 100%
	}

	.block {
	  width: 50px;
	  height: 50px;
	  margin: 5px;
	  cursor: pointer;
	  background: blue;
	  color: white;
	  font-size: 24px;
	  text-align: center;
	  line-height: 50px;
	}

	.active {
	  background: red;
	}

	.enter {
	  width: 100px;
	  height: 50px;
	  line-height: 50px;
	  text-align: center;
	  cursor: pointer;
	  background: #999999;
	  margin: 5px
	}

JavaScript

function q(e) {
  return document.querySelector(e)
}

function qq(e) {
  return document.querySelectorAll(e)
}

// Активация 
var btnSizes = qq(".block");
for (var i = 0, count = btnSizes.length; i < count; i++) {
  btnSizes[i].addEventListener("click", function() {
    this.classList.add("active");
  })
}


// Добавление в массив
var btnAdd = qq(".enter");
var array = [];
for (var i = 0, count = btnAdd.length; i < count; i++) {
  btnAdd[i].addEventListener("click", function() {
    let name = this.parentNode.querySelector(".name").innerText;
    let activeSize = this.parentNode.querySelector(".active").innerText;
    array.push([name, activeSize])
    console.log(array);
  })
}