JavaScript Set 6

Question 1

What is the filesystem module?

Answer 1

Allows you to work with the file system using node.js
require(“fs”);

Question 2

What functions can the file system module perform?

Answer 2

1. Read files
2. Create files
3. Update files
4. Delete files
5. Rename files

Question 3

What is the URL module?

Answer 3

Splits up a web address into readable parts

Question 4

What is the url.parse() method?

Answer 4

Returns a URL object with each part
Ex:
q = url.parse(adr)
log(q.host)
log(q.pathname)
log(q.search)

Question 5

What is the Node.js Crypto module?

Answer 5

Contains OpenSSL and allows you to encrypt and decrypt data
require(“crypto”);

Question 6

How can you encrypt data with the crypto module?

Answer 6

1. Create encryption cipher key with
   var key = crypto.Cipher(encryption method, key);
2. Encrypt the data with the key
   var cipherText = key.update(text, encoding method, return format);
3. Get any remaining encrypted data
   cipherText += key.final(return format)

Question 7

How can you decrypt data with the crypto module?

Answer 7

1. Create decryption key with
   var key = crypto.Decipher(encryption method, key);
2. Decrypt the data with the key
   var plainText = key.update(input text, input encoding, output encoding);
3. Get any remaining decrypted data
   plainText += key.final(output encoding);

Question 8

What does the dns module do?

Answer 8

Can convert URLs to IP addresses and vice-versa
require(“dns”);

Question 9

How do you convert a URL to an IP using the DNS module?

Answer 9

dns.lookup(URL, callback function (err, addresses, family));

Question 10

How do you convert an IP to a URL using the DNS module?

Answer 10

dns.reverse(IP, callback function (err, url));

Question 11

What does the events module do?

Answer 11

Allows you to create, fire, and listen for your own events
require(‘events’);

Question 12

How can you access event properties and methods?

Answer 12

By creating an EventEmitter object
var emitter = new events.EventEmitter();

Question 13

How do you assign an event handler to an event?

Answer 13

eventEmitter.on(event name, handler function);

Question 14

How do you fire an event?

Answer 14

eventEmitter.emit(event name);

Question 15

What does the timer module do?

Answer 15

Contains functions that can execute code after a certain period of time

Question 16

What are the 3 scheduling timer functions available in the timers module?

Answer 16

1. setImmediate() executes a function immediately
2. setInterval() executes a function every given milliseconds
3. setTimeout() executes a function after a given time in milliseconds

Question 17

What are the 3 cancelling timer functions available in the timers module?

Answer 17

1. clearImmediate() cancels and immediate object
2. clearInterval() cancels an interval object
3. clearTimeout() cancels a timeout object