const charsers = [
  { name: 'Nodejs', ranking: 7},
  { name: 'Reactjs', ranking: 7.5},
  { name: 'Vuejs', ranking: 6},
  { name: 'MongoDB', ranking: 7},
  { name: 'GraphQL', ranking: 7}
];


function order(list, orderType) {
  if (orderType === 'desc') {
    return list.sort((a, b) => a.ranking < b.ranking ? 1 : -1);
  }

  return list.sort((a, b) => a.ranking > b.ranking ? 1: -1);
}

function getAverage(list, propType) {
	const sum = list.map(item => item[propType]).reduce((prev, curr) => prev + curr, 0);
    return sum / list.length;
}

const result = order(charsers, 'asc');
const avarage = getAverage(charsers, 'ranking');