isPlainObject()

isPlainObject(value): value is Record<string, any>

Checks if a value is a plain object (object literal or Object.create(null)).

💎 Why is this a Hidden Gem?

Distinguishes true dictionaries from arrays, null, or class instances.

remarque

Excludes arrays, Date, Map, Set, class instances, etc. Only {}, new Object(), and Object.create(null).

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Parameters

value: unknown

The value to check.

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Returns: value is Record<string, any>

true if the value is a plain object, false otherwise.

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See Also

isObject

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Since

1.0.0

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Example

isPlainObject({});                    // => true
isPlainObject({ a: 1 });              // => true
isPlainObject(new Object());          // => true
isPlainObject(Object.create(null));   // => true
isPlainObject([]);                    // => false
isPlainObject(new Date());            // => false
isPlainObject(new Map());             // => false
isPlainObject(new (class Foo {})());  // => false
isPlainObject(null);                  // => false

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How it works?

Type guard that checks if a value is a plain object (object literal or Object.create(null)).

What Qualifies

Value	Result	Reason
{}	true	Object literal
{ a: 1 }	true	Object literal
new Object()	true	Object constructor
Object.create(null)	true	Null prototype
[]	false	Array
new Date()	false	Date instance
new Map()	false	Map instance
new MyClass()	false	Class instance
null	false	Not an object

isPlainObject vs isObject

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Use Cases

Identify configuration objects 📌

Ensure a value is a simple dictionary {} and not a complex object instance. Perfect for merging configs or validating JSON payloads.

#identify#configuration#dictionary#plain#objects#JSON

if (isPlainObject(config)) {
  // Safe to merge or spread
  const merged = { ...defaultConfig, ...config };
}

Deep clone decision logic

Determine if a value needs recursive cloning or can be copied by reference.

#clone#deep#recursion#copying#serialization#logic

function deepClone(value: unknown): unknown {
  if (!isPlainObject(value)) {
    return value; // Primitives, arrays handled elsewhere, class instances kept as-is
  }
  
  const result: Record<string, unknown> = {};
  for (const key in value) {
    result[key] = deepClone(value[key]);
  }
  return result;
}