Object Methods

Question 1

Object.assign()

Answer 1

Copies the values of all enumerable own properties from one or more source objects to a target object.

Question 2

Object.create()

Answer 2

Creates a new object with the specified prototype object and properties.

Question 3

Object.defineProperty()

Answer 3

Adds the named property described by a given descriptor to an object.

Question 4

Object.defineProperties()

Answer 4

Adds the named properties described by the given descriptors to an object.

Question 5

Object.entries()

Answer 5

Returns an array containing all of the [key, value] pairs of a given object’s own enumerable string properties.

Question 6

Object.freeze()

Answer 6

Freezes an object. Other code cannot delete or change its properties.

Question 7

Object.fromEntries()

Answer 7

Returns a new object from an iterable of [key, value] pairs. (This is the reverse of Object.entries).

Question 8

Object.getOwnPropertyDescriptor()

Answer 8

Returns a property descriptor for a named property on an object.

Question 9

Object.getOwnPropertyDescriptors()

Answer 9

Returns an object containing all own property descriptors for an object.

Question 10

Object.getOwnPropertyNames()

Answer 10

Returns an array containing the names of all of the given object’s own enumerable and non-enumerable properties.

Question 11

Object.getOwnPropertySymbols()

Answer 11

Returns an array of all symbol properties found directly upon a given object.

Question 12

Object.getPrototypeOf()

Answer 12

Returns the prototype of the specified object.

Question 13

Object.is()

Answer 13

Compares if two values are the same value. Equates all NaN values (which differs from both Abstract Equality Comparison and Strict Equality Comparison).

Question 14

Object.isExtensible()

Answer 14

Determines if extending of an object is allowed.

Question 15

Object.isFrozen()

Answer 15

Determines if an object was frozen.

Question 16

Object.isSealed()

Answer 16

Determines if an object is sealed.

Question 17

Object.keys()

Answer 17

Returns an array containing the names of all of the given object’s own enumerable string properties.

Question 18

Object.preventExtensions()

Answer 18

Prevents any extensions of an object.

Question 19

Object.seal()

Answer 19

Prevents other code from deleting properties of an object.

Question 20

Object.setPrototypeOf()

Answer 20

Sets the object’s prototype (its internal [[Prototype]] property).

Question 21

Object.values()

Answer 21

Returns an array containing the values that correspond to all of a given object’s own enumerable string properties.