Get a value from one array and add to remaining elements of both Array in JS

Question

Let's say I have the following 2 Arrays:

let a = [5,5,5,5,0]
let b = [5,5,5,5,0]

Assuming that both arrays has the same length:

I want to get a value from an element of one Array and add the +1 itself and to other remaining elements. If the the picked value is still bigger than zero, then it should also continue adding it to elements of other array from starting index.

Example_1: If I pick a[2] then the outcome should be:

a = [5,5,1,6,1] // a[2] became 0 after picking 5, then in each remaining element we add +1 and continue to next array.
b = [6,6,5,5,0]

Example_2: Or If I pick b[3] from initial arrays, then the outcome should be:

a = [6,6,6,5,0] // b[3] became 0 after picking 5, then in each remaining element we add +1 and move to next array until our value becomes zero
b = [5,5,5,1,1]

Here is my attempt:

let pickedValue = a[2]

for (let index = 2; index < a.length; index++) {
    if (pickedValue > 0) {
        a[index] += 1
        pickedValue--
    }
}
for (let index = 0; index < pickedValue; index++) {
    if (pickedValue > 0) {
        b[index] += 1
        pickedValue--
    }
}

Can we do this in more dynamic way with maybe one loop?

From your description I understand that every element can only increase, but in your example *a[2] became 0 after picking 5*, how? — Al.G., Mar 06 '22 at 15:46
Can you please rephrase this: *add the +1 itself and to other remaining elements*; I don't quite understand it. — Al.G., Mar 06 '22 at 15:48
@Al.G, a[2]=5 at first but after picking it became 0 then you start adding 5 to picked element and also remaining element so it became 1 — Angels, Mar 06 '22 at 15:49
@AnuragSrivastava added my attempt. Please remove the negative rating. — Angels, Mar 06 '22 at 16:08

score 1 · Answer 1 · answered Mar 06 '22 at 16:02

You just need to iterate through both arrays. The chosen array should be iterated from the target + 1 up to its lenght, and the other array, from 0 up the target. You can see that I directly put a 1 to the chosen array at index target, instead of put a 0 and add +1.

(Also use some regex in order to catch the number between the brackets, from this SO answer)

let a = [5,5,5,5,0]
let b = [5,5,5,5,0]


const ans = prompt("Pick an element (e.g `a[2]` or `b[3]`)");

const [chosenArray, otherArray] =  ans[0] === 'a' ? [a, b] : [b, a];
const target = parseInt(ans.match(/(?<=\[).+?(?=\])/), 10);

chosenArray[target] = 1;
for (let i = target + 1; i < chosenArray.length; ++i)
  ++chosenArray[i];
for (let i = 0; i < target; ++i) 
  ++otherArray[i];


console.log(a, b)

Thanks but this is not working if *a[2] = 9* as an example. – Angels Mar 08 '22 at 20:22 — Angels, Mar 08 '22 at 20:22
@Angels What should be the result for *a[2] = 9*? – AlexSp3 Mar 08 '22 at 21:07 — AlexSp3, Mar 08 '22 at 21:07

score 1 · Answer 2 · answered Mar 06 '22 at 17:02

You could tkae an object with same named properties of arrays and hand over target key and index and then update until no more value is to disperse.

const
    update = (source, target, index) => {
        const keys = Object.keys(source);
        let value = source[target][index];
        source[target][index] = 0;
        while (value--) {
            source[target][index++]++;
            if (index === source[target].length) {
                index = 0;
                target = keys[(keys.indexOf(target) + 1) % keys.length];
            }
        }
        return source;
    };

console.log(update({ a: [5, 5, 5, 5, 0], b: [5, 5, 5, 5, 0] }, 'a', 2));
console.log(update({ a: [5, 5, 5, 5, 0], b: [5, 5, 5, 5, 0] }, 'b', 3));

.as-console-wrapper { max-height: 100% !important; top: 0; }

Get a value from one array and add to remaining elements of both Array in JS

2 Answers2