# Create an empty map that does not have properties

An object with no prototype: no inherited keys such as toString or __proto__.

Canonical: https://1loc.dev/object/create-an-empty-map-that-does-not-have-properties/
Version: 1.0.0
Runtime: JavaScript · Node.js 22 / modern browsers
Verification: Usage lines executed in Node.js 22 and headless Chromium; no external services
Updated: 2026-10-28

## Implementation

```javascript
function createDictionary() { return Object.create(null); }
```

## Usage

```javascript
const counts = createDictionary();
'toString' in counts; // → false
'toString' in {}; // → true
counts.__proto__ = 'a key like any other';
Object.keys(counts); // → ['__proto__']
```

Lines marked → were executed in Node.js 22 and in headless Chromium, and each result was compared with the value shown. Lines marked e.g. are illustrative.

## Limits

- Keys from user input, such as "__proto__", stay ordinary data, as the last lines show.
- For keys added and removed at runtime, a Map is often clearer. JSON.stringify serializes a null-prototype object but turns a Map into {}.

The function does not validate its arguments. Add checks where it receives untrusted input.

## Source and license

Original: https://github.com/phuocng/1loc/blob/14b481cf60dff1620ab1bb99a43b1f68068cdd9b/contents/create-an-empty-map-that-does-not-have-properties.mdx
Author: Nguyen Huu Phuoc and original contributors
Contributors: See original repository history
Source commit: 14b481cf60dff1620ab1bb99a43b1f68068cdd9b
Copyright (c) 2020 phuoc-ng
License: MIT — https://1loc.dev/licenses/
Maintainer: Oveyon
Modifications: Documented as a reference with executed usage lines. Original MDX retained as inert source evidence.