Module 2 Flashcards
1
Q
What is a method?
A
A function that is a property of an object.
2
Q
How can you tell the difference between a method definition and a method call?
A
Function definition has structure function () { }, a call just has the function name and parameters, empty if none.
3
Q
Describe method definition syntax (structure).
A
an object, function keyword, parenthese for arguments, and codeblock
4
Q
Describe method call syntax (structure).
A
object.methodName()
5
Q
How is a method different from any other function?
A
Stored as a property of an object
6
Q
What is the defining characteristic of Object-Oriented Programming?
A
objects can contain both data (as properties) and behavior (as methods). You wrap functionality with the data structure (object).
7
Q
What are the four “principles” of Object-Oriented Programming?
A
abstraction, encapsulation, inheritance, polymorphism
8
Q
What is “abstraction”?
A
Simplifying a complex action into a simple one
9
Q
What does API stand for?
A
application programming interface
10
Q
What is the purpose of an API?
A
A software interface that offers services to other software. A way for one software to use another software’s data without having to know how the other software works. Like going to a restaurant and ordering food, you don’t need to know how to make it or how to request the chef, just need to know what you want.
11
Q
What is this in JavaScript?
A
An implicit parameter that changes depending on where in a function it is called. Usually refers to what object you are in.
12
Q
What does it mean to say that this is an “implicit parameter”?
A
It is something available to use in a code block even if it was never explicitly declared or included in its parameter list.
13
Q
When is the value of this determined in a function; call time or definition time?
A
Determined when the function is called.
14
Q
What does this refer to in the following code snippet?
var character = {
firstName: 'Mario',
greet: function () {
var message = 'It\'s-a-me, ' + this.firstName + '!';
console.log(message);
}
};
A
the character object
15
Q
Given the above character object, what is the result of the following code snippet? Why?
character.greet();
A
‘it’s-a-me, Mario!’ Because it calls the method in the object, which calls for a string plus the object firstName property with this.
16
Q
Given the above character object, what is the result of the following code snippet? Why? var hello = character.greet; hello();
A
‘it’s-a-me, undefined!’ Because ‘this’ refers to window since it is not directing to any object. Hello is only assigned the function greet, no connection to character object.
17
Q
How can you tell what the value of this will be for a particular function or method definition?
A
Impossible to tell because this is defined by when it is called. You can make a best guess if it is a method.
18
Q
How can you tell what the value of this is for a particular function or method call?
A
Find where the function is called and look for an object to the left of the dot.
19
Q
What kind of inheritance does the JavaScript programming language use?
A
Prototypal (prototype-based). Objects inherit from other objects.
Trivia: Most other programming languages are class-based, they inherit from classes rather than objects.
20
Q
What is a prototype in JavaScript?
A
Template that objects inherit properties and methods from
21
Q
How is it possible to call methods on strings, arrays, and numbers even though those methods don’t actually exist on objects, arrays, and numbers?
A
It has an existing prototype object in javascript
22
Q
If an object does not have it’s own property or method by a given key, where does JavaScript look for it?
A
it checks the first prototype then checks the prototype of that prototype and so on, until it finds it, or returns undefined.
23
Q
What does the new operator do?
A
It creates a new empty object then assigns that object’s prototype to be the prototype property of the constructor, then calls the constructor function assigning ‘this’, and if there is no return object for the function it uses ‘this’.
24
Q
What property of JavaScript functions can store shared behavior for instances created with new?
A
Prototype property. Note that function objects have their own properties that can be found. 5 total properties, see MDN.
25
What does the instanceof operator do?
Checks if the prototype property of a constructor appears anywhere in the prototype chain of the object.
26
What is a "callback" function?
A function passed into another function as an argument
27
Besides adding an event listener callback function to an element or the document, what is one way to delay the execution of a JavaScript function until some point in the future?
setTimeOut() or setInterval().
| Related ones: getAnimationFrame() and requestIdleCallback(), which adjust to how fast browser is running.
28
How can you set up a function to be called repeatedly without using a loop?
setInterval()
29
What is the default time delay if you omit the delay parameter from setTimeout() or setInterval()?
No delay. However, it is still asynchronous and anything without setTimeout() or setInterval() will run after anything that is not timed.
30
What do setTimeout() and setInterval() return?
an integer ID number which can be passed into clearTimeout()
31
What is a client?
The one that requests a service
32
What is a server?
Provider of resources or services to clients
33
Which HTTP method does a browser issue to a web server when you visit a URL?
GET method by default
34
What three things are on the start-line of an HTTP request message?
The method, path aka the request target, and the http method (protocol version).
Example format: PUT /create_page HTTP/1.1
35
What three things are on the start-line of an HTTP response message?
The http method (protocol version), status code (success or fail, 404 is a notable example), and status text description
36
What are HTTP headers?
They let the client or server pass additional information with a http request or response.
37
Where would you go if you wanted to learn more about a specific HTTP Header?
MDN, developer.mozilla.org/en-US/docs/Web/HTTP/Headers
38
Is a body required for a valid HTTP request or response message?
No. Request typically does not contain body. Response does not necessarily always have a body.
39
What is AJAX?
A technique for loading data into part of a page without having to reload an entire page.
40
What does the AJAX acronym stand for?
Asynchronous JavaScript And XML
41
Which object is built into the browser for making HTTP requests in JavaScript?
xmlhttpRequest()?
42
What event is fired by XMLHttpRequest objects when they are finished loading the data from the server?
'load' event
43
An XMLHttpRequest object has an addEventListener() method just like DOM elements. How is it possible that they both share this functionality?
It inherited this object prototype property?
44
What is destructuring, conceptually?
Turning the properties of an object or values of an array into individual variables
45
What is the syntax for Object destructuring?
let { property1: variable1, property2: variable2 } = object;
46
What is the syntax for Array destructuring?
let [ arrayItem1, arrayItem2, ...args ] = arrayName;
47
How can you tell the difference between destructuring and creating Object/Array literals?
destructuring is like a reverse of creating, appears like it is declaring the object or array first then assigning to a variable name.
48
What is the syntax for defining an arrow function?
(argument) => { argument function } or () => return or no parentheses for just one argument.
49
When an arrow function's body is left without curly braces, what changes in its functionality?
The end result is returned automatically without a return statement.
50
How is the value of this determined within an arrow function?
Determined at definition, unlike function keyword which determines at function call.
51
What is Node.js?
Program that runs JavaScript outside of a browser, powered by v8 the same as Chrome. it is wrapped in various apis that allow it to interact with the host operating system. Browser JS is very limited, aka "sandboxed" to browser. It is an application server and can run programs that do not need to be in a web browser.
52
What can Node.js be used for?
To build back ends for web applications, command line programs, run web servers, write desktop applications, write mobile applications, or any other automation.
53
What is a REPL?
Read–eval–print loop. Also termed an interactive toplevel or language shell, is a simple interactive computer programming environment that takes single user inputs, executes them, and returns the result to the user. Read means it interprets user input. Eval means it runs whatever the user inputs. Print means it returns a value, so it is undefined if nothing is specified. Loop means it can be done again afterwards.
54
When was Node.js created?
May 27 2009. Note how recent it is. But also this is long enough to be considered middle aged for a program.
55
What back end languages have you heard of?
JavaScript, Java, Python, C, C++, C#? Web backend: Node, PHP, Ruby. Most recent: Rust (Not specifically web, just improved C++)
56
What is a computer process?
Instance of computer program being executed by one or multiple threads.
57
What is a CLI?
Command Line Interface. Advantage: More control for automating and direct instructions. More computer and programmer friendly.
58
What is a GUI?
Graphic User Interface
59
Use of command line man
manual
60
Use of command line cat
concatenates file
61
Use of command line ls
lists files in directory
62
Use of command line pwd
print working directory
63
Use of command line man
Prints whatever you enter into terminal
64
Use of command line touch
Update when file was modified
65
Use of command line mkdir
Makes a new directory
66
Use of command line mv
Moves file or folder
67
Use of command line rm
Removes (deletes) file or folder. Add -r to recursively remove nested directories and their contents as well. -f forces it to do it all without confirming.
68
Use of command line cp
Copy file or folder
69
What are the three virtues of a great programmer?
1. Laziness: The quality that makes you go to great effort to reduce overall energy expenditure. It makes you write labor-saving programs that other people will find useful and document what you wrote so you don't have to answer so many questions about it.
2. Impatience: The anger you feel when the computer is being lazy. This makes you write programs that don't just react to your needs, but actually anticipate them. Or at least pretend to.
3. Hubris: The quality that makes you write (and maintain) programs that other people won't want to say bad things about.
70
Roughly how many computer processes are running on your host operating system (Task Manager or Activity Monitor)?
A lot- over 100.
71
Why should a full stack Web developer know that computer processes exist?
Most importantly so that you can kill a process if needed. See what ports are being taken up by a process, because one port can only be used by one webserver at a time. To be able to take full advantage of what can be done and to be aware of limitations.
72
What is the process object in a Node.js program?
Provides information about the current node process.
73
How do you access the process object in a Node.js program?
Console.log(process); the variable name process.
74
What is the data type of process.argv in Node.js?
An array of all modules.
75
What is a JavaScript module?
A single js file with its own scope.
76
What values are passed into a Node.js module's local scope?
exports, require, module, __filename, and __dirname
77
Give two examples of truly global variables in a Node.js program.
Buffer, console, process
78
What is the purpose of module.exports in a Node.js module?
It is the placeholder of what is returned from the module, specifies what you want to be available for another module to use
79
How do you import functionality into a Node.js module from another Node.js module?
Use the require() function with the module name.
80
What is the JavaScript event loop?
The way JavaScript treats processes which is with a queue of tasks that need to be completed before the next. First takes task, adds its code to call stack, resolves the stack, finishes the task, and takes it off the queue.
81
What is the difference between 'blocking' and 'non-blocking' code?
blocking vs nonblocking is like synchronous or asynchronous code. Blocking must be executed and finished one by one and will prevent the next from happening. Non blocking will start it, let code afterwards get added to task queue run, and if it finishes it is added back to task queue.
82
What is a directory?
The folder/file that points to other files.
83
What is a relative file path?
The location of the file relative to the current directory folder
84
What is an absolute file path?
The full directory file location starting from root element to end target file.
85
What module does Node.js include for manipulating the file system?
fs module, aka file system.
86
What method is available in the node.js fs module for writing data to a file?
fs.readFile
87
Are file operations of the fs module synchronous or asynchronous
Asynchronous
88
Which HTTP method does a browser issue to a web server when you visit a URL?
GET method
89
What is on the first line of an HTTP request message?
The http method, request target, and html version
90
What is on the first line of an HTTP response message?
The protocol version, status code, and status text that is meant for a human to understand
91
What are HTTP headers?
Lets client and server pass additional information in the request or response. It's usually meta information as key-value pairs.
92
What is NPM?
Node package manager, a way to upload, share, or download modules (aka packages) of code. Large software registry, and has command line interface.
93
What is a package?
A self contained collection of files that are needed or included for a library. Packages tend to contain multiple modules.
94
How can you create a package.json with npm?
Within the directory you want to create the json, type "npm init --yes" (notes -yes automatically says yes to all questions, should review next time if plan on publishing)
95
What is a dependency and how to you add one to a package?
It's another package that your code needs. Installing another module into your project directory and turning that directory into a package.
96
What happens when you add a dependency to a package with npm?
It gets added to package.json and downloads the package for that dependency and adds it to the modes module, and also all of its own dependencies.
97
How do you add express to your package dependencies?
npm install express
98
What Express application method starts the server and binds it to a network PORT?
listen(portNumber). Calling listen is what tells it to start receiving and responding to requests. Can't do anything to a server before that. Before this it is not really a server just software that's running.
99
How do you mount a middleware with an Express application?
Use app.method when express is imported and called and assigned to a variable app. Pass it a callback function with parameters req and res.
100
Which objects does an Express application pass to your middleware to manage the request/response lifecycle of the server?
req (request) and res (response)
101
What is the appropriate Content-Type header for HTTP messages that contain JSON in their bodies?
application/json; chartset=utf-8
102
What is the significance of an HTTP request's method?
It indicates the desired action to be performed on the identified source.
103
What does the express.json() middleware do and when would you need it?
It allows the server to parse json and is needed if the body information that you're sending and receiving are json format.
104
What are the http request methods?
get, post delete, put, patch
105
What is PostgreSQL and what are some alternative relational databases?
It is a relational database system (sql standing for structured query language). Others: MySQL, Microsoft Server, Oracle
106
What are some advantages of learning a relational database?
It has a long history and SQL databases are widely used, they are flexible, harder to make accidental changes, they can model data, maintain quality of stored data integrity
107
What is one way to see if PostgreSQL is running?
sudo service postgresql status, or top and see if it is running.
108
What is a database schema?
The collection of tables in a database and definitions of the tables like columns, but not the data within the tables.
109
What is a table?
The way data is stored in a relational database, which is a collection of rows that all have same set of attributes.
110
What is a row?
Single record in a table.
111
What is SQL and how is it different from languages like JavaScript?
It stands for structured query language and it is a way of interacting with relational databases. The difference is that it is declarative rather than imperative. You tell it what you want done, rather than tell it exactly what to do and how.
112
How do you retrieve specific columns from a database table?
You use the select declaration: select "columnName" from "tableName"
113
How do you filter rows based on some specific criteria?
You add the where declaration: where "condition" = 'value'
114
What are the benefits of formatting your SQL?
Easier readability
115
What are four comparison operators that can be used in a where clause?
greater than, less than, equal to, and not equal to.
116
How do you limit the number of rows returned in a result set?
Declare: limit number;
117
How do you retrieve all columns from a database table?
Declare: select *
118
How do you control the sort order of a result set?
Declare: order by "columnName" desc (default is ascending, descending is option to change order)
119
How do you add a row to a SQL table?
You declare: insert into "tableName" (columnName, etc.) values ('columnValue, etc')
120
What is a tuple?
List of values in a column with a fixed length, size, and meaning.
121
How do you add multiple rows to a SQL table at once?
Same as insert but add more values: values ('columnValue1'), ('columnValue2')
122
How do you get back the row being inserted into a table without a separate select statement?
Declare "returning *" at the end of inserting. to specify, do returning (value1, value2)
123
How do you update rows in a database table?
Declare: update "tableName" set "columnItem" = 'newValue'. Note this updates everything
124
Why is it important to include a where clause in your update statements?
So that you only update what you intend to and not the entire column in a table.
125
How do you delete rows from a database table?
Declare: delete from "tableName"
126
How do you accidentally delete all rows from a table?
Declaring delete from table without setting any restrictions on what to specifically delete
127
What is a foreign key?
A column with values that refer to a column in another table with the same column name
128
How do you join two SQL tables?
Declare: join "otherTable" using ("sharedColName")
129
How do you temporarily rename columns or tables in a SQL statement?
Using "as", declare: ... "tableName" as "t"; OR "columnName" as "newName". Alternatively: JOIN... ON... which uses multiple columns
130
How do you change which rows limit picks up?
offset declaration: tells it to skip the number then take rows afterwards.
131
What is a CRUD operation?
Create, read, update, delete
132
What are some examples of aggregate functions?
max(), min(), sum(), count(), every()
133
What is the purpose of a group by clause?
Tells the aggregate function how it should split its calculations among the rows
134
What are the three states that a promise can be in?
Pending: something that takes a while, not necessarily a request. Resolved: normal response. Rejected: Error returned
135
How do you handle the fulfilment of a promise?
Use then() method and a function as the first parameter, which runs when promise is resolved.
136
How do you handle the rejection of a Promise?
Can either use then() method with a function as the second argument, or use catch().
