OOP

Question 1

What is encapsulation

Answer 1

Bundling data and operations related to that data in a cohesive unit called an object

Question 2

What is OOP

Answer 2

A programming paradigm where we think of a problem in terms of objects

Question 3

Advantages of OOP

Answer 3

Programmers think of program at a higher-level of abstraction, reduce dependencies in a program, easy to understand

Question 4

Disadvantages of OOP

Answer 4

Often much larger than procedural programs, less efficient code - memory, computing power

Question 5

How is JS encapsulation different from other languages?

Answer 5

JS does not directly limit exposure to methods and properties.

Question 6

A factory function returns

Answer 6

an object

Question 7

One object factory can reuse another object factory by:

Answer 7

mixing object returned by other factory function into itself using object.assign

Question 8

forEach loops vs for loops

Answer 8

forEach loops over only ‘own’ properties. for loops over all the enumerable properties

Question 9

How do you create an object that doesn’t have a prototype?

Answer 9

Object.create(null)

Question 10

method to get prototype of an object

Answer 10

Object.getPrototypeOf(obj)

Question 11

What does enumerable mean?

Answer 11

The property will show up if you iterate over the object using a for loop or Object.keys

Question 12

What is an interface of an object?

Answer 12

The state and behaviors exposed by the object for other objects to use.

Question 13

What can you use as the value of a property in an object?

Answer 13

string, float, null, function object, another object. Any valid JS value

Question 14

What is a collaborator object and 2 examples.

Answer 14

They represent the connections between various actors in your program. A primitive value and an object that is part of the state of another object

Question 15

A benefit of collaborator objects

Answer 15

They let you chop up and modularize the problem domain into cohesive pieces.

Question 16

Use Object.create to

Answer 16

create a new object, using an existing object as the prototype of the newly created object

Question 17

Use Object.setPrototypeOf to

Answer 17

set the prototype of an object that already exists

Question 18

By default, all object literals inherit from

Answer 18

Object.prototype

Question 19

What built-in methods have we learned about that we can use to specify a function’s execution context explicitly?

Answer 19

call and apply

Question 20

bind returns

Answer 20

a new function permanently bound to first argument

Question 21

Global execution context is created when?

Answer 21

before any code is executed

Question 22

A new execution context gets created when

Answer 22

whenever a function is executed

Question 23

A downstream object can override a property if

Answer 23

it has a property with the same name

Question 24

Function invocations - execution context?

Answer 24

rely upon implicit execution context that resolves to the global object

Question 25

Method invocations - execution context?

Answer 25

implicit execution context - resolves to object connected to method

Question 26

The value of this is

Answer 26

The current execution context of a function or method

Question 27

Arrow functions are permanently bound to

Answer 27

the execution context of the enclosing function invocation (usually global object)

Question 28

Javascript has 1st class functions that can do these 3 things:

Answer 28

1) Add them to objects and execute them in that object 2) Remove them from their objects, pass around, and execute in other contexts 3) Dynamically bound to a context at execution time

Question 29

child object delegates invocation of a method call to parent object or other way around

Answer 29

child object delegates to parent object!

Question 30

Object.getPrototypeOf({}) returns

Answer 30

A reference to the default prototype object

Question 31

for loop will go through even the properties and methods that

Answer 31

aren't directly set in the new object

Question 32

Do all objects in JavaScript have an object prototype?

Answer 32

you can use Object.create(null) to create an object that doesn't have a prototype

Question 33

Can you hoist with a function declaration or a function expression

Answer 33

function declaration (where the word function comes first on the line)

Question 34

JavaScript runs programs in two passes;

Answer 34

the first pass performs hoisting, and the second executes the code.

Question 35

All JavaScript functions are

Answer 35

first-class entities.

Question 36

All arrow functions in JavaScript are

Answer 36

anonymous functions.

Question 37

How many functions can you pass to another function

Answer 37

as many as you want

Question 38

Any function can return

Answer 38

another function

Question 39

Higher-order functions are also

Answer 39

first-class values.

Question 40

A function that returns a function is

Answer 40

a higher-order function.

Question 41

A function that accepts one or more arguments that are themselves functions is

Answer 41

a higher-order function.

Question 42

When does JavaScript bind an object to this

Answer 42

When the function is executed using method-call syntax, e.g., foo.bar(). When the function is executed by either apply or call. When the function is executed using function-call syntax, e.g., bar()

Question 43

What naming convention separates constructor functions from other functions?

Answer 43

Constructor function names are capitalized.

Question 44

What is the static modifier?

Answer 44

A static method is defined directly on the class, not on the objects the class creates.

Question 45

All objects that have a length property are

Answer 45

array-like objects

Question 46

If A is a class, what does typeof A return

Answer 46

typeof A returns "function"

Question 47

JS is a what type of OO language?

Answer 47

Prototypal OO language. Meaning objects can inherit directly from other objects

Question 48

Pseudoclassical Inheritance uses

Answer 48

A constructor function and the 'new' operator to create objects and the 'prototype' property to build the inheritance chain. Also known as constructor inheritance

Question 49

Prototypal Inheritance is creating _______

Answer 49

a new object from an existing object, using object.create()

Question 50

An instance method or property is from

Answer 50

the object creator - like with the class Person, 'Daniel' would be an instance and we're talking about the methods and properties he has

Question 51

In OLOO objects inherit _

Answer 51

directly from other objects without constructor - subset of prototypal inheritance

Question 52

What is polymorphism

Answer 52

Polymorphism is the ability of an object to take on many forms. Objects share behaviors and override shared behaviors with specific ones. It uses inheritance to do this.

Question 53

Constructor function uses

Answer 53

this.argument (which can be property or method - methods are properties) and the new keyword

Question 54

Factory function returns

Answer 54

an object, just return and then argument separated by commas

Question 55

Built-in constructors examples are

Answer 55

Array, Object, String, Number

Question 56

The keyword new determines:

Answer 56

whether or not a function is a constructor

Question 57

What are collaborator objects - 2 points

Answer 57

``` First, collaborator objects can be of any type: custom class object, Array, Hash, String, Integer, etc Second, a collaborator object is part of another object’s state. ```

Question 58

How is multiple inheritance done

Answer 58

with mix-ins

Question 59

A mixin is a _______

Answer 59

Object (defined by const) containing methods that can be used by other classes

Question 60

Mixins vs inheritance

Answer 60

mix-in is a restricted case of multiple inheritance

Question 61

method invocation vs. function invocation

Answer 61

method invocation 'this' binds to the current object and when you call function invocation pattern 'this' binds to global object

Question 62

A higher order function is

Answer 62

a function that takes a function as an argument, or returns a function

Question 63

Global object is:

Answer 63

A global object is an object that always exists in the global scope

Question 64

execution context is

Answer 64

a concept that holds information about the environment within which the current code is being executed

Question 65

For every function call,

Answer 65

the JavaScript engine creates a new Function Execution Context. It creates the arguments object that contains a reference to all the parameters passed into the function

Question 66

bind is a property of

Answer 66

functions

Question 67

Implicit binding (functions) - what do you do?

Answer 67

Look to the left of the dot

Question 68

Explicit binding

Answer 68

Call, apply, or bind

Question 69

Context loss usually happens in

Answer 69

nested functions