JavaScript Object Methods

Question 1

What does `Object.keys()` return?

Accepted Answer

An array of an object's own enumerable property names

Answer

All properties including inherited ones

Answer

An array of the object's values

Answer

An array of [key, value] pairs

Question 2

What does `Object.assign()` do?

Accepted Answer

Copies all enumerable own properties from one or more source objects to a target object

Answer

Creates a deep clone of an object

Answer

Assigns a prototype to an object

Answer

Seals an object against modification

Question 3

What does `Object.freeze()` do?

Accepted Answer

Prevents all modifications — adding, deleting, or changing property values

Answer

Prevents new properties from being added but allows modification of existing ones

Answer

Creates an immutable deep clone of the object

Answer

Prevents the object from being garbage collected

Question 4

What does `Object.entries()` return?

Accepted Answer

An array of [key, value] pairs for own enumerable properties

Answer

An array of the object's own enumerable property values

Answer

A Map of the object's properties

Answer

An array of property descriptors

Question 5

What is the difference between `Object.seal()` and `Object.freeze()`?

Accepted Answer

`seal()` prevents adding/deleting properties but allows changing existing values; `freeze()` prevents all changes

Answer

They are identical

Answer

`freeze()` allows value changes; `seal()` prevents all changes

Answer

`seal()` is for arrays; `freeze()` is for objects

Question 6

What does `Object.create()` do?

Accepted Answer

Creates a new object with the specified object as its prototype

Answer

Creates a plain empty object like `{}`

Answer

Copies an object's properties to a new object

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Defines properties on an existing object