Loop through array of arrays and increment values into a new array

Question

I'm struggling with looping through an array of arrays and returning a new array with the incremented value of the result.

Here's the concept:

let array1 = [array1, array2];
let array2 = [4000,5000,3000,6000];
let array3 = [3000, 15000, 9000, 1000];
let i = 0;
let newArray = []
while (i < array1.length) {
// how do I get the combined value in a new array so that newArray[0] = 7000, newArray[1] = 20000 etc.
}

Array1 comes from an API and is an unknown number of arrays.

Answer 1

This should work for any number of sub arrays. Here it is assumed that array1 contains 4 arrays.

let array2 = [4000, 5000, 3000, 6000]
let array3 = [3000, 15000, 9000, 500]
let array4 = [5000, 15000, 4000, 2000]
let array5 = [6000, 25000, 5000, 8000]
let array1 = [array2, array3, array4, array5]
const result = array1.reduce((acc, curr) => {
 return acc.map((item, index) => item + curr[index])
})
console.log(result)

---

References:

• .reduce
• .map

• Henrik Harju: OK this does the job, need to read up on reduce and map to understand why its working.
• A1exandr Belan: It's clean and simple, but a little tweaked: result = array1.map((arr) => arr.reduce((acc, value) => acc + value))

Answer 2

In case number of elements is dynamic then,

let array1 = [[4000, 5000, 3000, 6000], [3000, 15000, 9000, 1000, 2000, 3000], [1000], [3000, 15000, 9000, 1000, 2000, 3000, 1000, 10000]];
let index = 0;
let newArray = [];
let maxElements = Math.max(...array1.map(arr => arr.length));
let arrayLength = array1.length;
while (index < maxElements) {
 let total = 0;
 for (let arrayIndex = 0; arrayIndex < arrayLength; arrayIndex++) {
 let element = array1[arrayIndex][index]
 if (element) total += element;
 }
 newArray.push(total);
 index++;
}
console.log(newArray)

Answer 3

You may need a nested loop. So basically you will iterate array1 which holds both array2 and array3 and then in newArray you will see if specific index has a value. If so then you will add value with previous one

let array2 = [4000, 5000, 3000, 6000];
let array3 = [3000, 15000, 9000, 1000];
let array1 = [array2, array3];
let i = 0;
let newArray = []
while (i < array1.length) {
 for (let j = 0; j < array1[i].length; j++) {
 // if index of new array is unoccupied then set a value there 
 if (!newArray[j]) {
 newArray[j] = array1[i][j]
 } else {
 // if index is occupied then add with previous value
 newArray[j] = newArray[j] + array1[i][j]
 }
 }
 i++;
}
console.log(newArray)

Answer 4

we used .map() to reference all of the element in an array, since our elements are also array but array of numbers and we want to add them all.. we use .reduce() method to add all of the array inside of our mapped array. result will be will still be an array, but the array inside it that consists of numbers are all added using reduce method. If you want to add everything.. just reduce it again. It will give a single value

a bit late but I hope this helps other peeps too

 function addAll(array) {
 return array.map((el) => {
 return el.reduce((acc, curr) => {
 return acc + curr;
 });
 });
}