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If the browser makes request from web server (Node) and the web server responded what kind of streams are these?
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Mar 14, 2020
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Section 1
(50 cards)
If the browser makes request from web server (Node) and the web server responded what kind of streams are these?
The request is readable and the response is writable, because it is done from the Nodes perspective.
Does greetA and greetB return the same Object? var greetA = require('./greet'); var greetB = require('./greet'); greet.js exports this: module.exports = new Greetr();
They are, because the required returns a cashed Object.
What does the fs module stand for?
File system
Is possible to use the exports without using the module?
Yes, but you have to mutate it. It's recommended to just use module.exports. exports.greet = function() { // code }
What is character encoding?
How characters are stored in binary. (The numbers (or code points) are converted and stored in binary.
What is a chunk?
A piece of data being sent through a stream. (Data is split in 'chunks' and streamed).
What is a template literal?
A way to concatenate strings in JS (ES6). Easier to work with than a bunch of strings concatenated wit '+'. Example: var greet = `Hello ${name}`;
Do the lines below output the same stuff? module.exports exports
Nope, due to by reference exports module points to a new Object.
What is cognitive load?
How many things you have to think about the same time.
What is error-first callback?
Callbacks take an error Object as their first parameter. (null if no error, otherwise will contain an Object defining the error)
What is the revealing module pattern?
Exposing only the properties and methods you want via an returned Object. var greeting = 'Hello world' function greet() { console.log(greeting) } module.exports = { greet: greet }
What is a first-class function?
Everything you can do with other types you can do with functions.
What is a module?
A reusable block of code, whose existence does not accidentally impact other code. JS does not have this (ES6 excluded).
What is a stream?
A sequence of data made available over time. (Pieces of data that eventually combine into a whole)
What two types of events does Node.js have?
System Events <- libuv (C++ Core) Custom Events <- Event Emitter (Javascript Core)
What does Sync stand for? var greet = fs.readFileSync(__dirname + '/greet.txt', 'utf8');
Synchronic approach, this is useful for reading config files.
What is ECMASCRIPT?
The standaard JavaScript is based on.
What is non-blocking?
Doing other things whiteout stopping your program from running.
What is a buffer?
A temporary holding spot for data being moved from one place to another (intentionally limited in size).
What is libuv and what does it do?
It's C++ library that deals with events happening in the operating system.
What does this do? var john = Object.create(person);
It create an empty object named john and inherits all properties and methods from the person Object.
What are magic strings?
A string that has some special meaning in our code. This is a bad practice, because it makes it easy for a typo to cause a bug, and hard for tools to help us find it.
Rewrite this using pipe. var fs = require('fs'); var readable = fs.createReadStream(__dirname + '/greet.txt'); var writable = fs.createWriteStream(__dirname + '/greetcopy.txt'); readable.on('data', function(chunk){ console.log(chunk.length); writable.write(chunk); });
var fs = require('fs'); var readable = fs.createReadStream(__dirname + '/greet.txt'); var writable = fs.createWriteStream(__dirname + '/greetcopy.txt'); readable.pipe(writable);
Match the names of the function types. function greet() { console.log('hi'); } greet(); function logGreeting(fn) { fn(); } logGreeting(greet); var greetMe = function() { console.log('hi'); }; greetMe();
// function statement function greet() { console.log('hi'); } greet(); // functions are first-class function logGreeting(fn) { fn(); } logGreeting(greet); // function expression (still first class) var greeterMe = function() { console.log('hi'); };
What is machine code (lang)?
Programming languages spoken by computer processors. Every program you run on your computer has been converted (compiled) into machine code.
What is an event listener?
It basically code that respond to an event.
A client asks for ... and a server performs ... .
services
What is binary data?
Data stored in binary (sets of 1s and 0s). The core of the math that computers are based on. Each one or zero is called a 'bit' or 'binary digit'.
Let say you have loaded a module using require('./greet.js'); that contains the following code. var greet = function(argument) { console.log('Hello!'); } Is possible to invoke the function expression in app.js?
Nope, this is done by design.
What is a byte?
8 bits, (eight 0s or 1s)
In what lang is Node written?
C++
What is a JS engine?
A program that converts JS code into something the computer processor can understand.
Why is this code running without './' without throwing an error? var util = require('util');
Because it is a native module.
How would you convert this JSON in node to Object and console.log the value of "en"? { "en": "Hello", "es": "Hola" }
var greetings = require('./greetings.json'); console.log(greetings.en);
What will be the output of console.log? var util = require('util'); function Person() { this.firstname = 'John'; this.lastname = 'Doe'; } Person.prototype.greet = function() { console.log('Hello ' + this.firstname + ' ' + this.lastname); } function Policeman() { this.badgenumber = '12345'; } util.inherits(Policeman, Person); var officer = new Policeman(); officer.greet();
Output: Hello undefined undefined utile.inherits just connects the prototypes The function below is never being called. function Person() { this.firstname = 'John'; this.lastname = 'Doe'; } Use: function Policeman() { Person.call(this); // <- this.badgenumber = '12345'; }
How would you make this available outside the module? var greet = function(argument) { console.log('Hello!'); }
module.exports = greet;
In what language are browsers written? Hint: and the DOM
C++
What five arrguments does the IIFE has that is created when a module is exported?
(function (exports, require, module, __filename, __dirname) { // module code })
What encoding is used here? var buf = new Buffer('Hello');
utf8, which is default
How woud read a file greet.txt that is located in the same folder. var fs = require('fs');
var fs = require('fs'); var greet2 = fs.readFile(__dirname + '/greet.txt', 'utf8', function(err, data) { console.log(data); });
How would you load module greet.js that is located in the same folder into the app.js file?
require('./greet.js');
What is a breakpoint?
A spot in our code where we tell a debugging tool to pause the execution of our code.
What is a pipe?
A pipe is connecting two streams by writing to one stream what is being read from another. (In Node you pipe from a Readable stream to a Writable stream)
Why does this work? var buf = new Buffer;
Because Buffer is global in Node.
What is native module?
A module that essentially resides in the lib folder that already given by Node.js.
What is a abstract (base) class?
A type of constructor you never work directly with, but inherit from. ( We create new custom Objects, which inherit from the abstract base class)
What is a character set?
A representation of characters as numbers. Each character gets a number. Unicode and ASCII are character sets.
What are commonJs modules?
An agreed upon standard for how code modules should be structured.
Section 2
(50 cards)
How would you replace the <h1>{Message}</h1> with the 'Hello world'. var http = require('http'); var fs = require('fs'); http.createServer(function(req, res) { res.writeHead(200, { 'Content-type': 'text/html' }); var html = fs.readFileSync(__dirname + '/index.htm'); res.end(html); }).listen(1337, '127.0.0.1');
var http = require('http'); var fs = require('fs'); http.createServer(function(req, res) { res.writeHead(200, { 'Content-type': 'text/html' }); var html = fs.readFileSync(__dirname + '/index.htm', 'utf8'); var message = 'Hello world...'; html = html.replace('{Message}', message); res.end(html); }).listen(1337, '127.0.0.1');
from package.json "dependencies": { "moment": "~2.11.2" } What does the '~' mean?
If a newer patch comes out, then automatically update it.
How would change the Mime type to JSON? res.writeHead(200, { 'Content-type': 'text/html' });
res.writeHead(200, { 'Content-type': 'application/json' });
How would you require a node_module called moment?
var foo = require('moment');
How would you npm install jasmine-node only for development?
npm install jasmine-node --save-dev
What is TCP?
TCP stand for Transmission control protcol. Defines how we send the defined protocol (no matter the protocol type, format). Splits the information into pieces that we are sending through the socket.
Name tree protocols that send data through a socket.
HTTP, FTP, SMTP
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What does ip mean?
Internet protocol
What is a socket?
A internet connection, the line across which the information flows.
What is a endpoint? (API)
One url in a web API. (Sometimes that endpoint (URL) does multiple thing by making choices based on the HTTP request headers.
Rewrite this using streams. var http = require('http'); var fs = require('fs'); http.createServer(function(req, res) { res.writeHead(200, { 'Content-type': 'text/html' }); var html = fs.readFileSync(__dirname + '/index.htm', 'utf8'); res.end(html); }).listen(1337, '127.0.0.1');
var http = require('http'); var fs = require('fs'); http.createServer(function(req, res) { res.writeHead(200, { 'Content-type': 'text/html' }); fs.createReadStream(__dirname + '/index.htm').pipe(res); }).listen(1337, '127.0.0.1');
How would you set view engine to ejs in express?
app.set('view engine' 'ejs');
What is a protocol?
A set of rules two sides agree on to use when communicating. Bothe the client and server are programmed to understand and use that particular set of rules. It is similar to two people from different countries agreeing on a language to peak in.
What standaard ip adres for the local system (localhost)?
127.0.0.1
What is an API?
A set of tools for building a software application. Stands for 'Application Programming Interface'. On the web the tools are usually made available via a set of URLs which accept and send only data via HTTP and TCP/IP.
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How would you install packages specified in package.js?
npm install
What is routing?
Mapping url request to content.
You have created a public folder and want to have static assets be available once browser requests /whatever. How would you do it using express?
app.use('/whatever', express.static(__dirname + '/public'));
How would you serve this JSON on the '/api' url? res.writeHead(200, { 'Content-type': 'application/json' }); var obj = { firstname: 'John', lastname: 'Doe' } res.end(JSON.stringify(obj));
if (req.url ==='/api') { res.writeHead(200, { 'Content-type': 'application/json' }); var obj = { firstname: 'John', lastname: 'Doe' } res.end(JSON.stringify(obj)); }
From what 3 things does a HTTP response consist of?
Status, Headers, Body
How would you respond with a 404 header? http.createServer(function(req, res) { // code here }).listen(1337, '127.0.0.1');
http.createServer(function(req, res) { res.writeHead(404); res.end(); }).listen(1337, '127.0.0.1');
How are the 3 versioning numbers called? 1.7.2
MAJOR.MINOR.PATCH 1.7.2 PATCH - bugs MINOR - new features MAJOR - big changes (code might break) more info: semver.org
What are static files?
Not dynamic, In other words, not precessed by code in any way.
from package.json "dependencies": { "moment": "^2.11.2" } What does the '^' mean?
If a newer minor or patch comes out, then automatically update it.
What does Node 'zlib' module do?
Allows to incorporate a compressed file.
When you npm init, you will get asked to add an entry point. What is that.
This is the file node will run. Mostly it is app.js.
What is a dependency?
Code that another set of code depends on to function. (If you use that code in your app, it is a dependency. Your app depends on it.)
How would you install npm nodemon glabaly?
npm install -g nodemon
Does the native http.js module deal with https?
No there is a separate module for that, https.js as you probably already guest.
What command line should use in order to create a package.json file?
npm init
How would you convert this Object to JSON? var obj = { firstname: 'John', lastname: 'Doe' }
var foo = JSON.stringify(obj);
How can you update npm modules?
npm update
What are environment variables in Node?
Global variables specific to the environment (server) our code is living in. Different servers can have different variable settings, and we can access those values in code.
What is MIMI type?
A standard for specifying the type of data being sent. Stands for 'Multipurpose Internet Mail Extensions'. Examples: application/json, text/html, image/jpeg.
What is http?
A set of rules (and a format) for data being transferred on the web. Stands for 'HyperText Transfer Protocol'. It is a format (of various) defining data being transferred via TCP/IP. Example of a HTPP request: CONNECT www.google.com:443 HTTP/1.1 Host: www.google.com Connection: keep-alive
How would you create a basic server in Node?
var http = require('http');
http.createServer(function(req, res) {
res.writeHead(200, { 'Content-type': 'text/plain' });
res.end('Hello world
');
}).listen(1337, '127.0.0.1');
Would work? app.get('/person/:page/:id', function(req, res) { });
Yes, you can have multiple
npm install moment --save What does --save do?
It saves the dependency reference to package.json.
What is middleware?
Code that sits between two layers of software. (In the case of Express, sitting between the request and the response.)
What does next(); do here? app.use('/', function(req, res, next){ console.log('Requst url: ' + req.url); next(); });
Call the next middleware that is connected to this route.
What do the HTTP headers do?
They carry information about the client browser, the requested page, the server and more.
What is a http method?
Specifies the type of action the request wishes to make. (GET, POST, DELETE, and others. Also called verbs.)
What does cli (folder found in node packages) stand for?
command line interface
What does to serialize mean?
To translate an Object into a format that can be stored or transferred. JSON, CSV, XML, and other are popular. 'Deserialize' is the opposite.
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When you talk about npm, you might be talking about two things. What are they?
The registry and ... the program.
What is a port, what does it do?
Once a computer receives a packet, how it knows what program to send it to. When a program is setup on the operating system to receive packets from a particular port, it is said that the program is 'listening' to that port.
Why is good to not store node_modules in repos?
Because we don't need to.
Section 3
(4 cards)