Applications.ge

Night mode
Sign up
Login
Modules
- Basics of Programming
- Problem Solving
- Git
- HTML
- CSS
- Sass
- JavaScript
- PHP
- Laravel
Meetings
Challenges
Projects
Tutorials
Channels
Notes
Resources

Applications.ge
Modules
- Basics of Programming
- Problem Solving
- Git
- HTML
- CSS
- Sass
- JavaScript
- PHP
- Laravel
Meetings
Challenges
Projects
Tutorials
Channels
Notes
Resources

Results: 1578

Notes

Newest first
Oldest first
Newest first(All)
Oldest first(All)

Select table comment

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'

by Valeri Tandilashvili

MySQL

Table comment

Set table comment

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'

by Valeri Tandilashvili

MySQL

Trait static property and function

A static property (trvar) can only be accessed using the classname (C1). But a static function (stfunc) can be accessed using the classname or the instance ($obj).

trait Counter {
    static $trvar=1;

    public static function stfunc() {
        echo "Hello world!"
    }
}

class C1 {
    use Counter;
}

print "\nTRVAR: " . C1::$trvar . "\n";   //prints 1

$obj = new C1();
C1::stfunc();   //prints  Hello world!
$obj->stfunc();   //prints Hello world!

by გიორგი უზნაძე

PHP

OOP

Traits

Deal with multiple traits conflicts CODE


trait A
{
    private function smallTalk()
    {
        echo 'a';
    }

    private function bigTalk()
    {
        echo 'A';
    }
}

trait B
{
    private function smallTalk()
    {
        echo 'b';
    }

    private function bigTalk()
    {
        echo 'B';
    }
}

trait C
{
    public function smallTalk()
    {
        echo 'c';
    }

    public function bigTalk()
    {
        echo 'C';
    }
}

class Talker
{
    use A, B, C {
        //visibility for methods that will be involved in conflict resolution
        B::smallTalk as public;
        A::bigTalk as public;

        //conflict resolution
        B::smallTalk insteadof A, C;
        A::bigTalk insteadof B, C;

        //aliases with visibility change
        B::bigTalk as public Btalk;
        A::smallTalk as public asmalltalk;
       
        //aliases only, methods already defined as public
        C::bigTalk as Ctalk;
        C::smallTalk as cmallstalk;
    }

}

(new Talker)->bigTalk();//A
(new Talker)->Btalk();//B
(new Talker)->Ctalk();//C

(new Talker)->asmalltalk();//a
(new Talker)->smallTalk();//b
(new Talker)->cmallstalk();//c

by გიორგი უზნაძე

PHP

OOP

Traits

Arrow function inside "map" function CODE

Regular anonymous function:

let numbers = [10, 100, 1000]

let doubled = numbers.map(function(x){
  return x * 2
})

document.write(doubled)

Alternative arrow function:

let doubled = numbers.map((x) => { return x * 2 })

If it's only a single line we don't need curly brackets and the keyword

return

let doubled = numbers.map((x) => x * 2);

If the arrow function has only one parameter, it does not need parentheses:

let doubled = numbers.map(x => x * 2);

Note: We only need

parentheses

if we had zero or more than one parameters

by Valeri Tandilashvili

JavaScript

Arrow functions

Functions

Arrow function CODE

Regular anonymous function:

// Anonymous function
document.addEventListener('click', function(){
  console.log('You clicked me!');
})

The same function with arrow function syntax

// Arrow function
document.addEventListener('click', () => {
  console.log('You clicked me!');
})

Even more minimalistic arrow function

// More minimalistic arrow function 
document.addEventListener('click', () => console.log('You clicked me!'))

by Valeri Tandilashvili

JavaScript

Arrow functions

function "call" CODE

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)

by Valeri Tandilashvili

JavaScript

Function functions

Variables added to the global WINDOW object CODE

Variable

lastName

declared by the keyword

let

is not added to the global

window

object. That is why the variable is equal to

undefined

// Declaring variable using keyword "var"
var firstName = "Jet"

// Declaring variable using keyword "let"
let lastName = "Li"

// Declaring variable without using any keyword
carMark = "Tesla"

function driveCar() {
  console.log(this.firstName + ' ' + this.lastName + ' is driving a car '+this.carMark)
}

driveCar()

The result will be:

Jet undefined is driving a car Tesla

Because declaring variable with

var

keyword and without any declaration keyword are the same. Both add the variable to the global

window

object. After running the above code, global object

window

will have

firstName

and

lastName

attributes

window.firstName;  // "Jet"
window.lastName;  // undefined
window.carMark;  // "Tesla"

by Valeri Tandilashvili

JavaScript

THIS

Default THIS context inside function CODE

this

inside

driveCar()

function refers to the global window object. Global variables

firstName

and

lastName

are added to the

window

object. That is why they are visible using the keyword

firstName = "Jack"
lastName = "Ma"

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

driveCar()

If we call the same 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)

by Valeri Tandilashvili

JavaScript

THIS

Context of THIS keyword CODE

this

inside

fn()

function refers to the global

window

object. That is why

firstName

and

lastName

attributes are not accessible using

this

keyword

let john = {
  firstName: 'John',
  lastName: 'Doe',
  driveCar() {
    function fn () {
      console.log(this.firstName + ' ' + this.lastName + ' is driving a car');  // "undefined undefined is driving a car"
      console.log(this);
    }
    fn(); // fn.call(this);
    console.log(this.firstName + ' ' + this.lastName + ' is driving a car'); 
    console.log(this)
  }
}

john.driveCar();

In order to fix the issue, one of the ways is to use

call

function and pass the object that we want

this

to refer to inside the

fn()

function

fn.call(this);

Inside

driveCar()

function

this

refers to the

john

object because it is called through

john

object

john.driveCar();

by Valeri Tandilashvili

JavaScript

THIS

The 10 Days of JavaScript

Results: 1578