// to calculate the sum of array elements
const sum_declarative = (arr) => {
  let result = 0;
  for (let i = 0; i < arr.length; i++) {
    result += arr[i];
  }
  return result;
};

console.log(sum_declarative([1,2,3]));

// calculate the sum of array elements
const sum_imperative = (arr) => arr.reduce((total, item) => total += item, 0);
console.log(sum_imperative([1,2,3]));