// const map = (arr, mapFunc) => {
//   const newArr = [];

//   for (let i = 0; i < arr.length; i++) {
//     newArr.push(mapFunc(arr[i]));
//   }

//   return newArr;
// }

// const arr = [1, 2, 3, 4, 5];
// const multiplied = map(arr, (x) => x * 2);

// console.log(multiplied); // [ 2, 4, 6, 8, 10 ]

// const filter = (arr, filterFunc) => {
//   const newArr = [];

//   for (let i = 0; i < arr.length; i++) {
//     if (filterFunc(arr[i])) {
//       newArr.push(arr[i]);
//     }
//   }

//   return newArr;
// }

// const arr = [1, 2, 3, 4, 5];
// const filtered = filter(arr, (x) => x % 2 === 0);

// console.log(filtered); // [ 2, 4 ]

const reduce = (arr, reduceFunc, initialValue) => {
  let accumulator = initialValue;

  for (let i = 0; i < arr.length; i++) {
    accumulator = reduceFunc(accumulator, arr[i]);
  }

  return accumulator;
}

const arr = [1, 2, 3, 4, 5];
const sum = reduce(arr, (acc, el) => acc + el, 0);
const concatenated = reduce(arr, (acc, el) => acc + el, '');

console.log(sum); // 15
console.log(concatenated); // '12345'