invert()

invert<T>(object): Record<T[keyof T], keyof T>

Creates a new object by swapping keys and values.

DUPLICATE VALUES

last key wins.

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Type Parameters

T: T extends Record<PropertyKey, PropertyKey>

The type of the input object.

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Parameters

object: T

The object to invert.

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Returns: Record<T[keyof T], keyof T>

A new object with keys and values swapped.

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Since

2.0.0

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Note

Only enumerable string keys are included (Symbol keys are ignored).

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Performance

O(n) time & space.

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Also known as

invert (Lodash, es-toolkit, Remeda, Radashi) · invertObj (Ramda) · ❌ (Effect, Modern Dash, Antfu)

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Example

invert({ a: 1, b: 2, c: 3 });
// => { 1: 'a', 2: 'b', 3: 'c' }

invert({ a: 1, b: 1, c: 2 });
// => { 1: 'b', 2: 'c' }

const statusCodes = { success: 200, notFound: 404 };
const codeToStatus = invert(statusCodes);
codeToStatus[200]; // => 'success'

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How it works?

Creates a new object by swapping keys and values.

Key-Value Swap

Duplicate Values

When values are duplicated, the last key wins:

Use Case: Lookup Table

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Use Cases

Build reverse enum lookups 📌

Create a reverse mapping from enum-like objects for bidirectional access. Essential for converting between display names and internal codes.

#build#reverse#enum#lookup#bidirectional#mapping

const StatusCode = { PENDING: 'P', APPROVED: 'A', REJECTED: 'R' };
const StatusLabel = invert(StatusCode);
// { 'P': 'PENDING', 'A': 'APPROVED', 'R': 'REJECTED' }

const label = StatusLabel[record.status]; // 'P' → 'PENDING'

Swap keys and values

Create a reverse lookup map from an object. Useful for bidirectional mapping (e.g., ID to Name and Name to ID).

#swap#keys#values#reverse#mapping#bidirectional

const idMap = { admin: 1, user: 2 };
const roleMap = invert(idMap); // { '1': 'admin', '2': 'user' }

Index by value

Quickly find the key associated with a specific value.

#index#value#lookup#search#find#key

const colors = { red: '#ff0000', blue: '#0000ff' };
const colorName = invert(colors)['#ff0000']; // 'red'