isPlainObject

Problem

You need to distinguish plain data objects from class instances, arrays, and built-ins — for example deciding whether to deep-merge or use as-is.

Solution

Use isPlainObject(value) to narrow to Record<string, unknown>. Returns true only for objects with Object.prototype or null prototype.

import { isPlainObject } from '@vielzeug/arsenal';

isPlainObject({}); // true
isPlainObject({ a: 1 }); // true
isPlainObject(Object.create(null)); // true

isPlainObject([]); // false — array
isPlainObject(new Date()); // false — class instance
isPlainObject(null); // false

Related

• isArray
• isNil