Invert keys and values of an object

Swap every key with its value.

JavaScript Version 1.0.0 · MIT · .md

function invert(object) { return Object.fromEntries(Object.entries(object).map(([key, value]) => [value, key])); }

Input & expected output

{
  "delivered": "250",
  "deferred": "451"
}

{
  "250": "delivered",
  "451": "deferred"
}

The edge case

{
  "a": "x",
  "b": "x"
}

{
  "x": "b"
}

Know the limits

• Values become string keys; duplicates keep the last key, as the edge case shows.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Keep exploring

• Pick properties from an object — Build a new object with only the requested own properties.
• Omit properties from an object — Keep the own enumerable fields that are not in a supplied list.
• Create an object from pairs of key and value — Turn [key, value] pairs into a plain object with Object.fromEntries.