Vanilla Counter Example

counter.js

let totalCount = 0;
let render = count => document.getElementById('count').innerHTML = count;

document.getElementById('increment')
  .addEventListener('click', () => {
      totalCount += 1;
      render(totalCount);
  });

document.getElementById('decerement')
  .addEventListener('click', () => {
      totalCount -= 1;
      render(totalCount);
  });

render(totalCount);