Array Reduce

array.reduce.js

const arr = [1, 2, 3, 4, 5];

// Without initial value
const sumOfArr = arr.reduce((acc, cur) => {
  return acc + cur;
});
console.log(sumOfArr);

// With initial value
const sumWithInitialValue = arr.reduce((acc, cur) => {
  return acc + cur;
}, 999); // 999 passed as second parameter of arr.reduce function
console.log(sumWithInitialValue);