Load CSS resource only for mobile devices

<link href="css/d1.m.min.css?t=2.9" rel="stylesheet" media="screen and (max-width: 500px)" type="text/css" />

Another way is to use

handheld

on

media

attribute

<link rel="stylesheet" type="text/css" href="mobile.css" media="handheld"/>

PHP's way to load CSS file for

mobile

devices

if(stristr($_SERVER['HTTP_USER_AGENT'], "Mobile")){
    echo '<link rel="stylesheet" href="style-400.css" type="text/css" />';
}

Load CSS resource only for desktop

<link href="css/d1.min.css?t=2.9" rel="stylesheet" media="screen and (min-width: 501px)" type="text/css" />

Another way is to use

screen

on

media

attribute

<link rel="stylesheet" type="text/css" href="screen.css" media="screen"/>

Using PHP

if(!stristr($_SERVER['HTTP_USER_AGENT'], "Mobile")){
    echo '<link rel="stylesheet" href="style.css" type="text/css" />';
}

Note: Remember this always loads the

d1.m.min.css

but activates it only on screens having max width as

500px

Get element (

input[type=text]

,

select

) value jQuery

let value = $("#element_id").val();

JS

let value = document.getElementById('element_id').value;'

Set value

5

to the specified element (

input[type=text]

,

select

) value jQuery

$("#element_id").val(5);

JS

let value = document.getElementById('element_id').value = 5;'

Check if the specified checkbox is checked jQuery

let is_checked = $("#element_id").is(":checked");

JS

let is_checked = document.getElementById('element_id').checked

Get HTML content of the specified element by element id jQuery

let content = $("#element_id").html();

JS

let content = 
 document.getElementById('element_id').innerHTML

Set HTML content to the specified element by element id jQuery

$("#element_id").html('some html');

JS

document.getElementById('element_id').innerHTML = 'some html'

Get attribute

placeholder

value of the element jQuery

$('#element_id').attr('placeholder');

JS

document.getElementById('element_id').getAttribute('placeholder');

Set attribute

placeholder

value to the specified element jQuery

$('#element_id').attr('placeholder', 'new placeholder');

JS

document.getElementById('element_id').placeholder = 'new placeholder';

Toggle class for an element jQuery

$("#element_id").toggle();

JS

document.getElementById('element_id').classList.toggle("hide");

CSS class

.hide {
	display: none !important;
}

Get selected

radio

value jQuery

let result = jQuery('input:radio[name=vote]:checked').val();

JS

let result = document.querySelector('input[name=vote]:checked').value;

Find

i

element inside another element with id

element_id

jQuery

let icon = $("#element_id").find('i');

JS

document.getElementById('element_id').querySelector('i');

Get

data-value

attribute of

datalist

element using selected text (datalist option's

value

attribute) jQuery

$('#datalist_id [value="selected text"]').data('value');

JS

document.querySelector('#datalist_id option[value="selected text"]').getAttribute('data-value')

Toggle two class for an element jQuery

let el = $('#element')
if(el.hasClass('arrow-down')) {
    el.removeClass('arrow-down');
    el.addClass('arrow-up');
} else {
    el.addClass('arrow-down');
    el.removeClass('arrow-up');
}

JS

let el = document.getElementById('element')
if (el.classList.contains('arrow-up')) {
    el.classList.remove('arrow-up');
    el.classList.add('arrow-down');
} else {
    el.classList.add('arrow-up');
    el.classList.remove('arrow-down');
}

Ajax request jQuery

$.ajax({
    url:'demo_get.asp',
    success:function(sms){
        $('#demo').html(sms);                        
    }
});

JS

var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
        document.getElementById("demo").innerHTML = this.responseText;
    }
};
xhttp.open("GET", "demo_get.asp", true);
xhttp.send();

MouseOver event jQuery

$('#element').on('mouseover', function(){
    console.log('mouse over');
});

JS

document.getElementById('element').addEventListener('mouseover', function(){
    console.log('mouse over');
});

Scroll animation down to the specified element's position in 500 ms jQuery

$('html, body').animate({scrollTop:($('#element').position().top)}, 400);

JS

function scrollDownToElement(el) {

    // Milliseconds per move 
    let pm = 50;

    // Padding from top
    let mft = 150;

    // Total animation milliseconds
    let scroll_ms = 500;

    // Calculates target element top position
    let bd_pos = document.body.getBoundingClientRect();
    let el_pos = document.getElementById(el).getBoundingClientRect();
    let height = el_pos.top-bd_pos.top-mft;

    // Calculates per move px
    let spm = height / (scroll_ms / pm);

    // The animation counter to stop
    let spmc = 1;
    let scroll_timer = setInterval(function() {

        // Moves down by {spm} px
        window.scrollBy(0, spm);
        spmc++;

        // Stops the animation after enough iterations
        if (spmc > (scroll_ms / pm)) {
            clearInterval(scroll_timer);
        }
    }, pm);
}
scrollDownToElement('element');

MySQL provides you with the DELETE JOIN statement that allows you to remove duplicate rows quickly. The following statement deletes duplicate rows and keeps the highest id:

DELETE t1 FROM table_name t1
INNER JOIN table_name t2 
WHERE 
    t1.id < t2.id AND 
    t1.email = t2.email;

The function sends ajax request with

vanilla JavaScript

and calls the

callback function

if the third parameter's type is

function

function ajax(url, methodType, callback){
    var xhr = new XMLHttpRequest();
    xhr.open(methodType, url, true);
    xhr.send();
    xhr.onreadystatechange = function(){
        if (xhr.readyState === 4 && xhr.status === 200){
            if (typeof callback === "function") {
                callback(xhr.responseText);
            }
        }
    }
}

Example of calling the above method

ajax(url, 'GET', function(resp) {
    console.log(resp);
})

The relationship caused problems We should not write this many to many relationship inside User's model if we use Spatie permissions package

public function roles()
{
    return $this->belongsToMany(Role::class, 'model_has_roles', 'model_id', 'role_id');
}

When trying to pull the latest commits, the error was

error: The following untracked working tree files would be overwritten by merge:
        app/Log.php

The solution that fixed the problem:

git add * 
git stash
git pull

live-sass-compiler

extension can generate either

compressed

or

expanded

version of

.css

files. Configuration for

expanded

version:

"liveSassCompile.settings.formats": [
    {
        "format": "expanded",
        "extensionName": ".css",
        "savePath": "/css/"
    }
]

Configuration for

compressed

version:

"liveSassCompile.settings.formats": [
    {
        "format": "compressed",
        "extensionName": ".min.css",
        "savePath": "/dist/css/"
    }
]

Using

CREATE

`keyword we can create different database objects. Creates database

university

CREATE DATABASE university

Creates table:

CREATE TABLE students (
    id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    first_name VARCHAR(100) NOT NULL,
    last_name VARCHAR(100) NOT NULL,
    email VARCHAR(50)
)

Creates database

user1

which will have password

some-pass

CREATE USER 'user1'@'localhost' IDENTIFIED BY 'some-pass';

returns

true

if

needle

is found inside

 haystack

inArray('find_me', ['text1', 'text2', 'find_me', 'text3']);

returns true

function inArray(needle, haystack) {
  var length = haystack.length;
  for(var i = 0; i < length; i++) {
      if(haystack[i] === needle) { return true };
  }
  return false;
}

SELECT from two tables

SELECT * FROM Table1;
SELECT * FROM Table2;

INNER JOIN

SELECT *
 FROM Table1 t1
INNER JOIN Table2 t2
   ON t1.fk = t2.id;

LEFT OUTER JOIN

SELECT *
 FROM Table1 t1
LEFT OUTER JOIN Table2 t2
 ON t1.fk = t2.id;

RIGHT OUTER JOIN

SELECT *
 FROM Table1 t1
RIGHT OUTER JOIN Table2 t2
 ON t1.fk = t2.id;

SEMI JOIN – Similar to INNER JOIN, with less duplication.

SELECT *
FROM Table1 t1
WHERE EXISTS (SELECT 1
               FROM Table2 t2
               WHERE t1.fk = t2.id
            );

ANTI SEMI JOIN

SELECT *
FROM Table1 t1
WHERE NOT EXISTS (SELECT 1  
                   FROM Table2 t2
                   WHERE t1.fk = t2.id
                );

LEFT OUTER JOIN with exclusion

SELECT *
 FROM Table1 t1
LEFT OUTER JOIN Table2 t2
  ON t1.fk = t2.id
WHERE t2.id is null;

RIGHT OUTER JOIN with exclusion

SELECT *
 FROM Table1 t1
RIGHT OUTER JOIN Table2 t2
  ON t1.fk = t2.id
WHERE t1.fk is null;

FULL OUTER JOIN

SELECT * FROM Table1 t1
 LEFT OUTER JOIN Table2 t2
  ON t1.fk = t2.id
UNION
SELECT * FROM Table1 t1
 RIGHT OUTER JOIN Table2 t2
  ON t1.fk = t2.id;

FULL OUTER JOIN with exclusion

SELECT * FROM Table1 t1
 LEFT OUTER JOIN Table2 t2
  ON t1.fk = t2.id
 WHERE t2.id IS NOT NULL
UNION
SELECT * FROM Table1 t1
 RIGHT OUTER JOIN Table2 t2
  ON t1.fk = t2.id
 WHERE t1.ID IS NOT NULL;

Two INNER JOINs

SELECT *
 FROM Table1 t1
INNER JOIN Table2 t2
  ON t1.fk = t2.id
INNER JOIN Table3 t3
  ON t1.fk_table3 = t3.id;

Two LEFT OUTER JOINS

SELECT *
 FROM Table1 t1
LEFT OUTER JOIN Table2 t2
  ON t1.fk = t2.id
LEFT OUTER JOIN Table3 t3
  ON t1.fk_table3 = t3.id;

INNER JOIN and a LEFT OUTER JOIN

SELECT *
 FROM Table1 t1
INNER JOIN Table2 t2
  ON t1.fk = t2.id
LEFT OUTER JOIN Table3 t3
  ON t1.fk_table3 = t3.id;