How to use

classList

function

in

Array

const selectTab = (tabHref) => {
 let allTabsInControlGroup = Array
  .from(document.querySelectorAll(`.js-select-tab[href="${ tabHref }"]`))
  .map(tabBtn => tabBtn.closest('.tab-menu'))
  .map(tabsSelector => Array.from(tabsSelector.querySelectorAll('.js-select-tab')));
 allTabsInControlGroup = [].concat.apply([], allTabsInControlGroup);  // flatten array
 allTabsInControlGroup.forEach((tabBtn) => {
  tabBtn.classList.toggle('active', tabBtn.getAttribute('href') === tabHref);
 });

 const selectedTab = document.querySelector(tabHref);
 const tabContainer = selectedTab.parentNode;
 if (!tabContainer) {
  selectedTab.classList.toggle('show');
  return;
 }
 Array
  .from(tabContainer.querySelectorAll('.tabs__content'))
  .forEach(tabContent => {
   tabContent.classList.toggle('show', tabContent === selectedTab);
  });
}