Advanced JavaScript

Question 1

What are Objects in Object-Oriented programming?

Answer 1

Objects are a way to categorize behavior and data

Question 2

What are objects in JavaScript?

Answer 2

They’re collections of named properties and methods, and they can be created on the fly using the object literal syntax

Question 3

What is a grouping of data and behavior into an object entity?

Answer 3

Encapsulation

Question 4

An object inherits properties and methods from another object.

Answer 4

Inheritance

Question 5

In JavaScript, what is prototypal inheritance?

Answer 5

This means that, when an object inherits from another, the parent object is known as the child’s prototype.

Question 6

What two references does an object maintain with prototypal inheritance?

Answer 6

Every object maintains a reference to its prototype and every object inherits from the global object object.

Question 7

What will JavaScript return if an object property doesn’t exist?

Answer 7

undefined

Question 8

How does multiple inheritance work in JavaScript?

Answer 8

Multiple objects can inherit from one single object, but one single object cannot inherit from multiple other objects although it can inherit from an object that inherits from another.

Question 9

What is the constructor pattern?

Answer 9

A function called a constructor is used to create new objects. Constructors are used in combination with the new keyword to create objects.

Question 10

What is this code doing?

var Person = function (name) {
    this.name = name;
};

var tom = new Person(‘tom’);

Answer 10

Implementing the constructor pattern to create new Person’s objects.

Question 11

What function makes it possible to create, modify and insert elements from JavaScript?

Answer 11

createElement

Example: var div = document.createElement(‘div’);

Question 12

What is the appendChild method used for?

Answer 12

All elements have the appendChild method that allows you to append an element to it.

Question 13

Each DOM element has a property that’s actually the DOM element’s parent. To remove an element, you call the ________ method of the parent, passing the child element you want to remove.

Answer 13

removeChild

Example: div.parentNode.removeChild(div);

Question 14

________ is a new DOM API for drawing on a 2- or 3-dimensional plane.

Answer 14

Canvas

Question 15

What is the 3D canvas web technology?

Answer 15

WebGL

Question 16

How does canvas animation work?

Answer 16

By repeatedly clearing the canvas (or a section of it) and redrawing the scene.

Question 17

Why is it very useful to be able to store information in the browser?

Answer 17

So that the information can be shared across different pages and browsing sessions.

Question 18

What are cookies?

Answer 18

Text files saved to a user’s computer.

Question 19

What is the difference between cookies and local storage?

Answer 19

Unlike cookies, local storage can only be read client-side — that is, by the browser and your JavaScript. If you want to share some data with a server, cookies may be a better option.

Question 20

How to save data with local storage?

Answer 20

localStorage.setItem

Example: localStorage.setItem(‘name’, ‘tom’);

Question 21

How to get data out of local storage?

Answer 21

localStorage.getItem

Example: var name = localStorage.getItem(‘name’);

Question 22

True or False? Local storage can only save strings.

Answer 22

True

Storing objects requires that they be turned into strings using JSON.stringify

That also means the object must be run through JSON.parse on the way out of local storage.

Question 23

_______ are often used to notify another piece of code that something went wrong when trying to carry out a task

Answer 23

Errors

Question 24

What is error creation also known as?

Answer 24

Throwing an error

Question 25

You can account for exceptions being thrown using a construct called a ________.

Answer 25

try-catch

Question 26

True or False? If an error is thrown in the try block it doesn’t prevent continued code execution

Answer 26

The error is passed into the catch block for you to deal with.

Question 27

Are error objects?

Answer 27

Yes. The error passed to the catch block (like a function) is an object with a message property you can use to see what went wrong.

Question 28

How should your code handle errors?

Answer 28

In almost all cases you’ll want to ensure your code handles errors gracefully. It’s worth learning when errors are likely to occur so that you can defend your code against them.

Question 29

What keyword is used to generate errors?

Answer 29

throw

Question 30

What is a good way to avoid errors?

Answer 30

Being defensive in your code with try-catch blocks and checking the type of input data received from users.

Question 31

________ are used to search and match strings.

Answer 31

Regular Expressions.

Question 32

What is regular expression literal syntax?

Answer 32

Regular expression literal syntax is designated by two forward slashes. Everything between is the expression:.

Example: var regex = /^[a-z\s]+$/;

Question 33

What string methods accept regular expressions?

Answer 33

1. ) match

2. ) replace

Question 34

What is a ‘g’ flag used in regular expressions?

Answer 34

global flag that means the expression should match all occurrences, rather than just the first, which is what it does by default.

Question 35

Where do flags go in regular expressions?

Answer 35

Flags like ‘g’ or ‘i’ always go after the closing slash.

Example: text.replace(/(every|no)thing/gi, “something”);

Question 36

A ________ is a function that returns a function.

Answer 36

A closure

Question 37

In a closure which function is returned?

Answer 37

The inner function is returned and has access to the outer function’s variables due to functional scope.

Question 38

_________ is a platform for building servers in JavaScript, built on Google’s V8 JavaScript engine

Answer 38

Node

Question 39

What is npm?

Answer 39

Node Package Manager used to install others’ modules to make developing things easier.

Question 40

What is the key concept in software engineering is the idea of modularity in code?

Answer 40

Separating out the key functionality of your app. In a modular system a component can be swapped out at little cost, so long as the interface between the components remains the same. Similarly, different components can be worked on in isolation from each other.

Question 41

What is a sandbox?

Answer 41

Modules can be connected in a number of different ways - one way is with modules communicating only with a central event and resource management module, sometimes referred to as a sandbox, and not communicating directly with each other.

Question 42

What is Model-View-Controller (MVC) architecture is a way of structuring code within an application?

Answer 42

Model-View-Controller (MVC) architecture is a way of structuring code within an application.

1. ) A model is concerned with the data in your app
2. ) A view with displaying or outputting data
3. ) A controller with the business logic and coordinating the models and views