Copies all files and folders from

source_dir

to

destination_dir

cp -r /home/user/source_dir/. /var/www/html/destination_dir/

-r

- copies recursively (with subfolders and files)

.

- copies all files and folders inside the folder

If the URL starts with

https

it will make a request on

443

$ch = curl_init("https://xdatavpn.example.com/Bank");

If it starts with

http

the request will use

80

port

$ch = curl_init("http://xdatavpn.example.com/Bank");

Shows details about each column from

decorations

table including column comments

SHOW FULL COLUMNS FROM decorations

Selects

is_optional

column comment which exists in

decorations

table using

information_schema

database

SELECT COLUMN_COMMENT 
FROM information_schema.COLUMNS 
WHERE TABLE_SCHEMA = 'geiger' 
    AND TABLE_NAME = 'decorations' 
    AND COLUMN_NAME = 'is_optional'

Sets new comment for

name

column in

channels

table

ALTER TABLE `channels` CHANGE `name` `name` varchar(255) COMMENT 'name of channel'

Selects comment of

channels

table which exists in the

geiger

database

SELECT table_comment 
FROM INFORMATION_SCHEMA.TABLES 
WHERE table_schema='geiger' 
    AND table_name='channels'

Sets comment for the specified table to make it easy for other developers what the purpose of this table is

ALTER TABLE `the_table_name` comment 'Some text about the table'

If we call

driveCar()

function using

call()

function,

this

will refer to the object that will be passed. In this case:

john

object

let john = {
  firstName: 'John',
  lastName: 'Doe'
}

function driveCar() {
  document.write(this.firstName + ' ' + this.lastName + ' is driving a car<br/>')
}

driveCar.call(john)

The function

filter

filters the array members based on the

getNames

function condition

let myFavoritePlanets = [
    {name: 'Earth', radius: 6371}, 
    {name: 'Jupiter', radius: 69911}, 
    {name: 'Neptune', radius: 24622, moons: ['Triton', 'Thalassa', 'Nereid', 'Proteus', 'Hippocamp', 'Naiad']}
]
let biggerPlanetsNames = myFavoritePlanets.filter(getNames);

function getNames(planet) {
  return planet.radius > 20000
}
console.log(biggerPlanetsNames );

Function

splice

changes content of an array. Let's first create an array of integers

let myFavoriteNumbers = [5, 14, 16, 18, 23, 25, 27, 50, 70]

If we want to remove one element from an array, we need to pass

1

as the second argument and the index of the item as the first argument. In this example

14

(second item) will be removed by passing

1 and 1

as arguments

myFavoriteNumbers.splice(1, 1);  // [5, 16,18, 23, 25, 27, 50, 70]

To remove two adjacent items, we need to pass first item's index

2

and quantity of items

2

that we want to remove. In this example we want to remove

18

and

23

from the array at the same time

myFavoriteNumbers.splice(2, 2);  // [5, 16, 25, 27, 50, 70]

Replaces 3 items starting from index 2 with

27

,

29

and

31

myFavoriteNumbers.splice(2, 2, 27, 29, 31);  // [5, 16, 27, 29, 31, 50, 70]

Removes all the items of the array except the first and the last items

myFavoriteNumbers.splice(1, 5);  // [5,70]

Adds the two new items

100

and

200

to the array after the first item

myFavoriteNumbers.splice(1, 0, 100, 200);  // [5, 100, 200, 70]