Reduce to return a specific value while supplying an initial value-CodePudding

Hi I have the following object I am reducing to the key that its value is the greatest:

project.approved_account_ids: {
    "sp02.testnet": 3,
    "sp03.testnet": 1
}

Like so..

<Typography variant="body2">
  Architect: {Object.keys(project.approved_account_ids).reduce((a, b) => project.approved_account_ids[a] > project.approved_account_ids[b] ? a : b)}
</Typography>}

But if the object is like

project.approved_account_ids: {}

I get the error - TypeError: Reduce of empty array with no initial value. Which I know it is because there is not always keys and values to reduce.

I tried adding an initial value at the end like

{Object.keys(project.approved_account_ids).reduce((a, b) => project.approved_account_ids[a] > project.approved_account_ids[b], 0 ? a : b)}

But that doesn't work. What would be the best method to check if there are values in the first place before applying reduce()? Any help would be appreciated!!

CodePudding user response：

Assuming that you just want the highest value, so just the actual number?

Used Object.entries() on the object found here: obj.project.approved_account_ids

Object.entries(obj).reduce(
// Obj is now an array of pairs: [[key, val], [key, val],...]

Next set the initial value to a phony pair: ["key",-1] and then compare that initially which of course be replaced on the first iteration:

(max, [key, val]) =>
    max[1] > val ? max : [key, val], ["key", -1]
// Note the second param is destructured to a pair [key, val]

Return the second value of the highest pair: output[1]

In regards to an empty object or no number values it will not fail it will return -1 instead, see objB in example. Also, Object.values() works as well, but decided on Object.entries() just in case the actual key matters as well.

const obj = {
  project: {
    approved_account_ids: {
      "sp02.testnet": 3,
      "sp03.testnet": 1,
      "sp00.testnet": null,
      "sp04.testnet": 5,
      "sp05.testnet": 3
    },
    pending_account_ids: {}
  }
};

const objA = obj.project.approved_account_ids;

const objB = obj.project.pending_account_ids;


function maxV(obj) {
  let output = Object.entries(obj).reduce(
    (max, [key, val]) =>
    max[1] > val ? max : [key, val], ["key", -1]
  )
  return output;
}

console.log('Returning the highest number: maxV(objA)[1]');
console.log(maxV(objA)[1]);

console.log('Returning from an empty object: maxV(objB)[1]');
console.log(maxV(objB)[1]);

console.log('Returning the key of the highest number: maxV(objA)[0]');
console.log(maxV(objA)[0]);

console.log('Returning the key and the highest number as an array: maxV(objA)');
console.log(maxV(objA));

console.log('Returning the key and the highest number as an object: Object.fromEntries([[...maxV(objA)]])');
console.log(Object.fromEntries([[...maxV(objA)]]));