Converting Array of Pairs into 2 Separate Arrays Without Iteration

Question

I have an array of pairs that looks like this [[x,y], [x,y] ... ]. I want to format it into an Object where the values are arrays of x and y values like so {keys: [x1, x2, x3 ...], values: [y1, y2, y3 ... ]}.

Are there any array/object operations to complete this operation without iterating through the original list?

Answer 1

The easiest and safest way is to reduce the array to an object, although it requires a loop:

const input = [[3, 300], [2, 200], [1, 100]];

const result = input.reduce((acc, [key, val]) => {
  acc.keys.push(key);
  acc.values.push(val);
  
  return acc;
}, { keys: [], values: [] });

console.log(result);

I wouldn't actually use the convert to object / Map method (under Original Answer), because it has a serious caveat - duplicate entries the has the same keys would be overridden.

For example:

const input = [[3, 300], [3, 200], [3, 100]];

const obj = Object.fromEntries(input);
const result = { keys: Object.keys(obj), values: Object.values(obj) };

console.log(result);

Original Answer

Building on top of pilchard's answer, I would convert the array to a Map, and then take the Map's keys, and values. I would use a Map, and not an object, because object's keys are always strings, and if the values are integers, the object would also be sorted by their value. A Map would preserve the original type, and won't reorder them.

const input = [[3, 300], [4, 200], [1, 100]];

const map = new Map(input);
const result = { keys: [...map.keys()], values: [...map.values()] };

console.log(result);

An example of converting the same structure to an object:

const input = [[3, 300], [4, 200], [1, 100]];

const obj = Object.fromEntries(input);
const result = { keys: Object.keys(obj), values: Object.values(obj) };

console.log(result);