Object

Question 1

Object.prototype.hasOwnProperty()

Answer 1

Determine whether the object has property as a direct property.

params: prop

Note: In contrast with in, this does not check down the property chain

Question 2

Object.getOwnPropertyNames()

Answer 2

Returns all property names (enum or not) that are direct properties

params: obj

Question 3

Object.assign()

Answer 3

Copy values of all enumerable own properties from source(s) to target object and return target object

params: target, …sources

Question 4

Object.create()

Answer 4

Create a new object with proto and properties

params: proto[, propertiesObject]

propertiesObject
an object with enum own properties specifying property descriptors

Question 5

Object.defineProperties()

Answer 5

Defines new or modifies existing properties directly on object. Returns the object.

params: obj, props

Question 6

Object.defineProperty()

Answer 6

Define a new or modify an existing property directly on an object. Returns the object.

params: obj, prop, descriptor

obj
    the object to modify
prop
    the prop name 
descriptor
    An object with
 data descriptors:
      - configurable (required, defaults to false)
      - enumerable (required, defaults to false)
      - value
      - writable
    and accessor descriptors:
      - get
      - set

Question 7

Object.freeze()

Answer 7

Prevents new properties from being added, existing properties from being deleted or changed

params: obj

Question 8

Object.getOwnPropertyDescriptor()

Answer 8

Returns a property descriptor for an own property

params: obj, prop

Question 9

Object.getOwnPropertyNames()

Answer 9

Returns an array of all own string properties (enum or not)

params: obj

Question 10

Object.getOwnPropertySymbols()

Answer 10

Returns as array of all own symbol properties

params: obj