Ad. Javascript.info part 1

Question 1

An object is a ________________.

Answer 1

collection of properties and has a single prototype object.

Question 2

The prototype of an object may be ______ or ______

Answer 2

either an object or the null value

Question 3

A prototype of an object is referenced by the hidden internal _________ and property

Answer 3

[[Prototype]]

Question 4

A finite chain of objects which is used to implement inheritance and shared properties

Answer 4

Prototype chain

Question 5

code reuse stylistics is called the

Answer 5

class-based inheritance

Question 6

is the actual object that is used in the lookup chain to resolve methods, etc.

Answer 6

__proto__ or [[prototype]]

Question 7

is the object that is used to build __proto__ when you create an object with new:

Answer 7

prototype

Question 8

If the property is not found after the whole prototype chain lookup, then ________ is returned.

Answer 8

undefined value

Question 9

Object.prototype itself also has a __proto__, which is the final link of a chain and is set to______.

Answer 9

null

Question 10

a constructor function does another useful thing — it automatically sets a ___________ for newly created objects.

Answer 10

prototype object

Question 11

function Foo(y) {
  this.y = y;
}

// inherited property "x" using constructor
\_\_\_\_\_\_\_\_\_\_\_\_\_\_= 10;

Answer 11

Foo.prototype.x

Question 12

every object has a prototype

TRUE / FALSE

Answer 12

TRUE

Question 13

An object specifies its prototype via the internal property_________

Answer 13

[[Prototype]]

Question 14

What constitute a prototype chain are the __proto__ pointing up the chain, and the objects pointed to by __proto__, such as going from foo.__proto__, going up to foo.__proto__.__proto__, and so forth, until _______

Answer 14

null is reached.

Question 15

By default, JavaScript engine provides the Object() funtion and an anonymous object that can be referenced to via the ________

Answer 15

Object.prototype.

Question 16

The Object.prototype object has many built-in properties such as toString(), valueOf(), etc. It also has a property named_______ that points back to the _________

Answer 16

constructor

Object() function

Question 17

console.log(Object.prototype.constructor !== Object); //

Answer 17

false

Question 18

console.log(Object.prototype.constructor === Object); //

Answer 18

true

Question 19

let point = {
x: 10,
y: 20,
};

how many properties?
how many __proto__?

Answer 19

2 properties

1 __proto__

Question 20

Every object, when is created, receives it’s ______

Answer 20

prototype

Question 21

If the prototype is not set explicitly, objects receive _________as their inheritance object.

Answer 21

default prototype

Question 22

// Base object.
let point = {
  x: 10,
  y: 20,
};

// Inherit from `point` object.
let point3D = {
  z: 30,
  \_\_proto\_\_: point,
};

inherited or own

console.log(
  point3D.x, // 10,
  point3D.y, // 20,
  point3D.z  // 30,
);

Answer 22

inherited

inherited

own

Question 23

a delegation object used to implement prototype-based inheritance.

Answer 23

protoype

Question 24

finite chain of objects used to implement inheritance and shared properties.

Answer 24

prototype chain

Question 25

a mechanism used to resolve a property in the inheritance chain. The process happens at runtime, hence is also called dynamic dispatch.

Answer 25

delegation

Question 26

delegation

Answer 26

a mechanism used to resolve a property in the inheritance chain. The process happens at runtime, hence is also called dynamic dispatch.

Question 27

another name for delegation

Answer 27

dynamic dispatch.

Question 28

let empty = {};

console.log(empty.x);

Answer 28

// undefined

Question 29

To create a prototype-less dictionary, we have to explicitly set its prototype to ______

Answer 29

null

Question 30

// Doesn't inherit from anything.
let dict = \_\_\_\_\_\_\_\_\_\_

Answer 30

Object.create(null);

Question 31

let dict = Object.create(null);

console.log(dict.toString); //

Answer 31

undefined

Question 32

let protoA = {x: 10};
let protoB = {x: 20};

CREATE OBJECTC WRITE USING __PROTO__

console.log(objectC.x); // 10

Answer 32

let objectC = {__proto__: protoA};

Question 33

let protoA = {x: 10};
let protoB = {x: 20};

CREATE OBJECTC WRITE USING .CREATE

console.log(objectC.x); // 10

Answer 33

let objectC = Object.create(protoA);

Question 34

let protoA = {x: 10};
let protoB = {x: 20};

// Change the delegate to protoB DONT USE __PROTO__

console.log(objectC.x); // 20

Answer 34

Object.setPrototypeOf(objectC, protoB);

Question 35

When several objects share the same initial state and behavior, they form a________

Answer 35

classification

Question 36

________ is a formal abstract set which specifies initial state and behavior of its objects.

Answer 36

a class

Question 37

var a = {}; 
Object.getPrototypeOf(a); //
alert(a.\_\_proto\_\_);

Answer 37

[object Object]

Question 38

a________ function creates objects, and also automatically sets the prototype for its newly created instances

Answer 38

constructor

Question 39

Object is an unordered or ordered collection of key-value pairs.

Answer 39

unordered

Question 40

function A() {
  this.x = 10;
  return [1, 2, 3];
}

var a = new A();
console.log(a.x, a);

Answer 40

undefined, [1, 2, 3]

Question 41

function A() {}
var a = new A();
console.log(a.constructor); // 
console.log(a.constructor === A); //

Answer 41

function A() {}, by delegation

true

Question 42

As opposed to object literals, here, you define an object type without any specific values. Then, you create new object instances and populate each of them with different values.

Answer 42

constructor function

Question 43

4 ways to create a object

Answer 43

with object literals
using a constructor function
with ECMAScript 6 classes
with the Object.create() method

Question 44

The use of __proto__ is controversial, and has been discouraged.

TRUE / FALSE

Answer 44

TRUE

Question 45

Allows the addition of properties to all objects of type Object.

Answer 45

Object.prototype

Question 46

Object.prototype has a value of

Answer 46

1

Question 47

What are the 4 characteristics of Protypal Inheritance in JavaScript

Answer 47

• Prototype Chain - behavior is delegated up the prototype chain if it is not available on the new object
• .prototype links the function to an object
• [[Prototype]] internally links one object to another (not public)
• __proto__ (dunder proto) “public property” a getter function which returns the prototypal linkage of THIS

Question 48

The __________ is considered outdated and somewhat deprecated (in browser-only part of the JavaScript standard).

Answer 48

__proto__

Question 49

Object.getPrototypeOf(obj) –

Answer 49

returns the [[Prototype]] of obj (same as __proto__ getter).

Question 50

returns the [[Prototype]] of obj (same as __proto__ getter).

Answer 50

Object.getPrototypeOf(obj) –

Question 51

Object.setPrototypeOf(obj, proto) –

Answer 51

sets the [[Prototype]] of obj to proto (same as __proto__ setter).

Question 52

sets the [[Prototype]] of obj to proto (same as __proto__ setter).

Answer 52

Object.setPrototypeOf(obj, proto) –

Question 53

In JavaScript, objects have a special HIDDEN property __________ (as named in the specification), that is either null or references another object.

Answer 53

[[Prototype]]

Question 54

Object constructors are used to create an _________

Answer 54

instance of an object

Question 55

in Javascript every function expression is a _____

Answer 55

constructor.

Question 56

WHAT IS MISSING

let x = function ( ) {
this.k = k;
}

Answer 56

( k )

Question 57

__proto___ means what?

Answer 57

parent or creator

Question 58

Whats a prototype in Javascript?

Answer 58

a property that every function you create in javascript has, that points to an object

Question 59

the entity behind almost all objects_______

Answer 59

Object.prototype.

Question 60

Object.getPrototypeOf({}) ==Object.prototype);

Answer 60

true

Question 61

Object.getPrototypeOf(Object.prototype)

Answer 61

null

Question 62

The _____________ is an internal linkage that tight one object to another.

Answer 62

double bracket [[Prototype]]

Question 63

A constructor is called with the _____ keyword.

Answer 63

new

Question 64

A constructor names must start with a _________

Answer 64

capital letter

Question 65

function Foo() {}
var f = new Foo();
Object.getPrototypeOf(f) === Foo.prototype

TRUE / FALSE

Answer 65

TRUE

Question 66

This is what type of of object

Function User(firstName, lastName, dateOfBirth) {
      this.firstName = firstName;
      this.lastName = lastName;
      this.dateOfBirth = dateOfBirth;
}

var user001 = new User(“John”, “Smith”, 1985);

Answer 66

CONSTRUCTOR FUNCTIONS

Question 67

This is what type of of object

var user001 = {
   firstName: "John",
   lastName: "Smith",
   dateOfBirth: 1985,
   getName: function(){
      return "User's name: " + this.firstName + " " + this.lastName;
   }
};

Answer 67

OBJECT LITERALS

Question 68

This is what type of of object

class User {
   constructor(firstName, lastName, dateOfBirth) {
      this.firstName = firstName;
      this.lastName = lastName;
      this.dateOfBirth = dateOfBirth;

      this.getName = function(){
          return "User's name: " + this.firstName + " " + this.lastName;
      }
   }
}

var user001 = new User(“John”, “Smith”, 1985);

Answer 68

ECMASCRIPT 6 CLASSES

Question 69

This is what type of of object

var user001 = {
   firstName: "John",
   lastName: "Smith",
   dateOfBirth: 1985,
   getName: function(){
      return "User's name: " + this.firstName + " " + this.lastName;
   }
};

var user002 = Object.create(user001);

user002.firstName = “Jane”;

Answer 69

THE OBJECT.CREATE() METHOD

Question 70

Make a blank object using the Object() constructor:

var d =

Answer 70

new Object();

Question 71

Make a blank object using Object.create() method set to null

var d =

Answer 71

Object.create(null);

Question 72

Make a blank object using the bracket’s syntactig

var d =

Answer 72

{}

Question 73

You can find instanceof relationships by comparing a function’s prototype to an object’s ________ chain, and you can break these relationships by changing prototype.

Answer 73

__proto__

Question 74

_________is a property of a Function object

Answer 74

prototype

Question 75

Two ways to point to a prototype

Answer 75

__proto__

Object.getPrototypeOf( )

Question 76

function Point(x, y) {
    this.x = x;
    this.y = y;
}
var myPoint = new Point();

WRITE THE REVERSE:
myPoint instanceof Point;
myPoint instanceof Object

Answer 76

myPoint.__proto__ == Point.prototype

myPoint.__proto__.__proto__ == Object.prototype

Question 77

function Point(x, y) {
    this.x = x;
    this.y = y;
}
var myPoint = new Point();

WRITE THE REVERSE:
myPoint.__proto__ == Point.prototype
myPoint.__proto__.__proto__ == Object.prototype

Answer 77

myPoint instanceof Point;

myPoint instanceof Object

Question 78

let f = new function ()
let o = new object ()
let a = new array (0

ALL in hertiate from:

Answer 78

object.prototype

Question 79

Function objects inherit from ________

Answer 79

Function.prototype.

Question 80

Funtion.protype inherits from

Answer 80

object.prototype

Question 81

to look up the prototype chain we use _______

Answer 81

__proto__

Question 82

with constructor functions we dont need the _____ keyword

Answer 82

return

Question 83

function createCircle (radius){
return {
    radius,
    draw () {
        console.log('draw');
    }
};
}

What type of function?

Answer 83

factory

Question 84

____________ is the default toString representation of an object in javascript.

Answer 84

[object Object]

Question 85

Function objects:

stringify(function (){}) ->

Answer 85

[object Function]

Question 86

Array objects:

stringify([]) ->

Answer 86

[object Array]

Question 87

RegExp objects

stringify(/x/) ->

Answer 87

[object RegExp]

Question 88

Date objects

stringify(new Date) ->

Answer 88

[object Date]

Question 89

Object objects!

stringify({}) ->

Answer 89

[object Object]

Question 90

4 pillars (concepts of OOP)

Answer 90

encapsulation
abstraction
inheritance
polymorphism

Question 91

encapsulation does

Answer 91

reduce complexity + increase reusability

Question 92

abstraction

Answer 92

reduce complexity + isolate impact of change

that hides the internal implementation details

Question 93

inheritance

Answer 93

eliminate redundant code

Question 94

polymorphism

Answer 94

refactor switch / case statement

Question 95

What are the 3 Attributes of Object Data Properties?

Answer 95

1. Configurable - tells if you can delete or change
2. Enumerable - can be returned in a for/in loop
3. Writable - property can be changed

Question 96

Difference between class and an object?

Answer 96

An object is an instance of a class. Objects hold any information , but classes don’t have any information. Definition of properties and functions can be done at class and can be used by the object.

Class can have sub-classes, and an object doesn’t have sub-objects.

Question 97

typeof Object
//

Answer 97

‘function’

Question 98

typeof new Object()
//

Answer 98

‘object’

Question 99

The__________ method is a special method for creating and initializing an object created within a class.

Answer 99

constructor

Question 100

function A() {}
var a = new A(); 
console.log(a.constructor); //

Answer 100

ƒ A() {}

Question 101

function A() {}
var a = new A(); 
console.log(A.constructor); //

Answer 101

ƒ Function() { [native code] }

Question 102

Object.prototype.a = 5;

var v = {};
console.log(v.a); //

Answer 102

5

Question 103

prototype of Object.prototype can be altered

TRUE OR FALSE

Answer 103

TRUE