hasIn()

hasIn(object, key): boolean

Checks if path is a direct or inherited property of object.

DEPRECATED

Use the in operator directly instead.

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Parameters

object: object | null | undefined

The object to query.

key: string

The key to check.

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Returns: boolean

true if key exists, else false.

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See Also

in operator - MDN

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Since

2.0.0

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Also known as

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

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Example

// ❌ Deprecated approach
hasIn({ a: 1 }, 'a');         // => true
hasIn({ a: 1 }, 'toString');  // => true (inherited)

// ✅ Recommended approach
'a' in { a: 1 };              // => true
'toString' in { a: 1 };       // => true (inherited)

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How it works?

Checks if key exists as direct or inherited property.

Inheritance Check

Common Checks

Object	Key	Result
{a: 1}	'a'	true
{a: 1}	'toString'	true (inherited)
{a: 1}	'b'	false
null	'a'	false

Deprecated: Use the in operator directly.

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Use Cases

Check property exists 📌

Check if property exists on object.

#has#property#check#exists

"key" in obj;
// or
Object.hasOwn(obj, "key");

Safe property access

Check before accessing.

#safe#access#optional#chaining

if ("user" in data && "name" in data.user) {
  return data.user.name;
}

Optional chaining alternative

Use optional chaining instead.

#optional#chaining#null#safe

data?.user?.name;