[JavaScript] innerText, parseInt

innerText

 

parseInt

 

 

<h2 id="number">0</h2>
<div>
  <button id="increase">+1</button>
  <button id="decrease">-1</button>
</div>

const number = document.getElementById('number');
const increase = document.getElementById('increase');
const decrease = document.getElementById('decrease');

increase.onclick = () => {
  const current = parseInt(number.innerText, 10);
  number.innerText = current + 1;
};

decrease.onclick = () => {
  const current = parseInt(number.innerText, 10);
  number.innerText = current - 1;
};