Total up the instances of items in an array.

const data = ['bmw', 'bmw', 'lamborghini', 'audi', 'lamborghini', 'bmw', 'audi'];

const counting = data.reduce((obj, itm) => {
  if (!obj[itm]) {
    obj[itm] = 0;
  }
  obj[itm]++;
  return obj;
}, {});

console.log(counting);
// {bmw: 3, lamborghini: 2, audi: 2}