Identify top users/purchases

top_users.js

function idBestUsers() {
  let monthlyOrders = [...arguments];
  let totalMonths = monthlyOrders.length;
  let clientOrders = new Object();

  
  monthlyOrders[0].forEach(clientId => {
      if(!clientOrders[clientId]) {
          clientOrders[clientId] = new Array(monthlyOrders.length);
          clientOrders[clientId][0] = 0;
      }
      clientOrders[clientId][0]++;
  });

  var month;
  for (month = 1; month < totalMonths; month++) {
      monthlyOrders[month].forEach(clientId => {
          if(clientOrders[clientId]) {
              if(!clientOrders[clientId][month]) {
                  clientOrders[clientId][month] = 0;
              }
              clientOrders[clientId][month]++;
          }
      });
  }
  
  for (var clientId in clientOrders) {
      var totalOrdersForClient = 0;
      var everyMonth = true;
      var orders = clientOrders[clientId];
      
      for(var month = 0; month < totalMonths; month++) {
          if(!orders[month]) {
              everyMonth = false;
              break;
          }
          totalOrdersForClient += orders[month];
      }
      
      if (everyMonth) {
          clientOrders[clientId] = totalOrdersForClient;
      } else {
          delete clientOrders[clientId];
      }
  }
  
  var clientsByOrderTotal = new Object();
  
  Object.keys(clientOrders).forEach(clientId => {
      var clientTotal = clientOrders[clientId];
      if(!clientsByOrderTotal[clientTotal]) {
          clientsByOrderTotal[clientTotal] = [clientId];
      } else {
          clientsByOrderTotal[clientTotal].push(clientId);
      }
  });
  
  var clientsByOrderTotalArray = Object.keys(clientsByOrderTotal).map(total => [parseInt(total), clientsByOrderTotal[total]]);
  
  clientsByOrderTotalArray.forEach(a => a[1].sort());
  
  return clientsByOrderTotalArray.sort((a, b) => b[0] - a[0]);
}