accounts-frontend/packages/app/services/loader.js

// On page initialization loader is already visible, so initial value is 1
let stack = 1;

export default {
  show() {
    if (++stack >= 0) {
      const loader = document.getElementById('loader');

      if (!loader) {
        throw new Error('Can not find loader element');
      }

      loader.classList.add('is-active');
    }
  },

  hide() {
    if (--stack <= 0) {
      stack = 0;
      const loader = document.getElementById('loader');

      if (!loader) {
        throw new Error('Can not find loader element');
      }

      loader.classList.remove('is-active', 'is-first-launch');
    }
  },
};