How would I reverse combinate?

[matthew-dean]

Let's say I have a dataset like this:

[
  {"admin": true, "color": "red", "mode": "light"},
  {"admin": true, "color": "blue", "mode": "light"},
  {"admin": true, "color": "green", "mode": "light"},
  {"admin": false, "color": "red", "mode": "light"},
  {"admin": false, "color": "blue", "mode": "light"},
  {"admin": false, "color": "green", "mode": "light"},
  {"admin": true, "color": "red", "mode": "dark"},
  {"admin": true, "color": "blue", "mode": "dark"},
  {"admin": true, "color": "green", "mode": "dark"},
  {"admin": false, "color": "red", "mode": "dark"},
  {"admin": false, "color": "blue", "mode": "dark"},
  {"admin": false, "color": "green", "mode": "dark"}
]

How would I reverse the combination process to produce:

{
  color: ["red", "blue", "green"],
  admin: [true, false],
  mode: ["light", "dark"],
}

I'm not expecting this tool to do it; I just wondered if you might have some insight.

[marvin-j97]

@matthew-dean

function reverseCombinations<T, O extends Record<string, T>>(perms: O[]): Record<keyof O, T[]> {
  const sets: Record<string, Set<O[keyof O]>> = {};

  for (const perm of perms) {
    for (const key in perm) {
      if (!(key in sets)) {
        sets[key] = new Set();
      }
      sets[key].add(perm[key]);
    }
  }

  return Object.fromEntries(
    Object.entries(sets).map(([key, set]) => [key, Array.from(set)])
  ) as Record<keyof O, T[]>;
}