countOnly.js

// const assertEqual = require('./assertEqual.js').assertEqual;


const countOnly = function(allItems, itemsToCount) {

  const result = {};

  for (const item of allItems) {
    if ((item in itemsToCount) && itemsToCount[item]) {
      if (item in result) {
        // Above if statement can be done as result[item] which will be false if undefined is returned
        result[item]++;
      } else {
        result[item] = 1;
      }
    }
  }

  return result;
};

module.exports = countOnly;

// const firstNames = [
//   "Karl",
//   "Salima",
//   "Agouhanna",
//   "Fang",
//   "Kavith",
//   "Jason",
//   "Salima",
//   "Fang",
//   "Joe"
// ];

// const result1 = countOnly(firstNames, { "Jason": false, "Karima": true, "Fang": true });

// assertEqual(result1["Jason"], undefined);
// assertEqual(result1["Karima"], undefined);
// assertEqual(result1["Fang"], 2);