How do I loop through multidimensional arrays with forEach or .reduce?-CodePudding

I am trying to write a function called twoDimensionalProduct(array) that takes in a 2D array of numbers as an argument. The function should return the total product of all numbers multiplied together.

I can solve this using nested traditional for loops. This was my solution:

function twoDimensionalProduct(array){
  let prod = 1;
  for(let i = 0; i < array.length; i  ){
      let subArr = array[i];
      for(let j = 0; j < subArr.length; j  ){
          prod *= subArr[j]
      }
  }
  return prod
}

let arra1 = [
  [6, 4],
  [5],
  [3, 1]
];
console.log(twoDimensionalProduct(arra1)); // 360

I am trying to figure out how to solve the same problems using the forEach or reduce method. Can someone help me with the best approach to this?

CodePudding user response：

If you like one liners, here's how you do it in one line.

let arra1 = [
  [6, 4],
  [5],
  [3, 1]
];

let sum = arra1.flat(2).reduce((sum, val) => sum * val);
console.log(sum);

CodePudding user response：

Flatten the array and then reduce over the numbers.

function twoDimensionalProduct(array){
  return array.flat().reduce((acc, c) => acc * c);
}

let arra1 = [[6, 4],[5],[3, 1]];

console.log(twoDimensionalProduct(arra1));

CodePudding user response：

You can map the array to multiply within elements using reduce and finally reduce on the outer array

const prod = arra1.map((arr) => {
    return arr.reduce((a, b) => a * b);
}).reduce((a, b) => a * b);
console.log(prod);