JQuery VS JavaScript Presentation

VS

Basic Concepts

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var vs let vs const

1. var variables can be updated and re-declared;    let variables can be updated but not re-declared; const variables can neither be updated nor re-declared.

2. var and let can be declared without being initialized, const must be initialized during declaration.

var vs let vs const

3. var is function scoped, while let and const are block scoped.

function fun() {
  if (true) {
    var x = 0;
  }
  for (let i = 0; i < 10; i++) x++;
  console.log(x); // 10
}
fun();
console.log(x); // Error: x is not defined
function fun() {
  if (true) {
    let x = 0;
  }
  for (let i = 0; i < 10; i++) x++;
  console.log(x); // Error: Uncaught ReferenceError: x is not defined
}
fun();

Hoisting

`var`s and `function`s are hoisted.

console.log(x === undefined); // true
var x = 3;
let x = sum(1, 2);
function sum(a, b) {
  return a + b;
}
console.log(x); // 3

var x;
console.log(x === undefined); // true
x = 3;

same as

Hoisting

let and const hoisting is a special case named the "temporal dead zone".

To keep it simple, let's consider them not hoistable.

Conclusion

For reliable and traceable code, avoid using var. Instead use let and const.

Data types

  • Boolean
  • Number
  • BigInt
  • String

All primitive types, except null, can be tested by the typeof operator. typeof null returns "object", so use === null to test for null instead.

  • Symbol
  • Object
  • Undefined
  • Null

JavaScript has eight data types:

Data types

  • Array
  • Date

  • RegExp

  • Map

In JavaScript, functions are first-class objects, because they can be passed to other functions, returned from functions, and assigned to variables and properties. They can also have properties and methods just like any other object. What distinguishes them from other objects is that functions can be called.

  • Set
  • Error
  • Promise
  • Function

JavaScript also has some special object data types:

function sum() {
  return sum.a + sum.b;
}
sum.a = 1;
sum.b = 2;
sum(); // returns 3

Truthy and Falsy values

console.log(Boolean(true)); // true
console.log(Boolean(1)); // true
console.log(Boolean(' ')); // true
console.log(Boolean([])); // true
console.log(Boolean({})); // true
console.log(Boolean(function () {})); // true

Truthy:

console.log(!!false); // false
console.log(!!0); // false
console.log(!!''); // false
console.log(!!null); // false
console.log(!!undefined); // false
console.log(!!NaN); // false

False:

== vs ===

let a = 1,
  b = '1';

console.log(a == b); // true
console.log(a === b); // false

String Interpolation

const firstName = 'John',
  lastName = 'Doe';

const plusConcat = 'Hi 👋🏽, My name is ' + firstName + ' ' + lastName + '.';
const templateLiteralConcat = `Hi 👋🏽, My name is ${firstName} ${lastName}.`;

NaN (Not a Number)

const notANumber = 'Not a number';
console.log(Number.isNaN(notANumber)); // false
console.log(Number.isNaN(Number(notANumber))); // true

const num = 1_000_000;
console.log(Number.isNaN(+num)); // false

Arrow functions

// Traditional function fxpression
function add1(a, b) {
    return a + b;
}

// Arrow function
const add2 = (a, b) => {
  return a + b;
};

// One-line arrow function
const add3 = (a, b) => a + b;

Array functions

const arr = [1, 2, 3, 4, 5];
arr.length = 3;
console.log(arr); // [1, 2, 3]
arr.length = 0;
console.log(arr); // []

Use lenght to empty an array:

Filter array:

const arr = [0, 1, '', ' ', null, undefined, NaN, {}, []];
const filteredArr = arr.filter((val) => !!val);

Map:

const numbers = [1, 2, 3];
const squared = numbers.map((num) => num * num); // [1, 4, 9]

forEach:

const fruits = ['apple', 'banana', 'orange'];
fruits.forEach((fruit, index) => console.log(`fruit at "${index}": ${fruit}`));

`slice` vs `splice`

let numbers = [1, 2, 3, 4, 5];

// slice
const slicedArr = numbers.slice(1, 4);
console.log(slicedArr); // [2, 3, 4]
console.log(numbers); // [1, 2, 3, 4, 5]

// splice
const splicedArr = numbers.splice(1, 3);
console.log(splicedArr); // [2, 3, 4]
console.log(numbers); // [1, 5]

numbers = [1, 2, 3, 4, 5];
const splicedArr2 = numbers.splice(1, 3, 6, 7, 8);
console.log(splicedArr2); // [2, 3, 4]
console.log(numbers); // [1, 6, 7, 8, 5]

Slice extracts a copy, while splice delete from the array, and event adds to it if you want to.

`for...in` vs `for...of`

let list = [4, 5, 6];
const obj = { x: 1, y: 2, z: 3 };

for (let i in list) console.log(i); // "0", "1", "2",
for (let i in obj) console.log(i); // "x", "y", "z"

for (let i of list) console.log(i); // "4", "5", "6"
for (let i of obj) console.log(i); // TypeError: obj is not iterable

`for...in` iterates over all enumerable property keys of an object.

 

`for...of` iterates over the values of an iterable object.

Destructuring

const person = { name: 'John Doe', age: 30, gender: 'male' };

// Traditional way
const name = person.name,
  age = person.age,
  gender = person.gender;

// With destructuring
const { name, age, gender } = person;

Objects: 

const fruits = ['Apple', 'Banana', 'Orange'];

// Traditional way
const firstFruit = fruits[0],
  secondFruit = fruits[1],
  thirdFruit = fruits[2];

// Destructing
const [firstFruit, secondFruit, thirdFruit] = fruits;

Arrays:

Destructuring with default values

const person = { name: 'John Doe', gender: 'male' };
const { name, age = 18, gender } = person;

Objects: 

const fruits = ['Apple', 'Banana'];
const [firstFruit, secondFruit, thirdFruit = 'Orange'] = fruits;

Arrays:

Destrucurting with default values works with undefined values only, null is not included.

Spreading (Spread operator)

const originalArray = [1, 2, 3];
const copiedArray = [...originalArray];

console.log(copiedArray); // [1, 2, 3]
const arr1 = [1, 2, 3],
  arr2 = [4, 5, 6];

const mergedArr1 = arr1.concat(arr2),
  mergedArr2 = [...arr1, ...arr2];

console.log(mergedArr2); // [1, 2, 3, 4, 5, 6]
console.log(mergedArr1); // [1, 2, 3, 4, 5, 6]

Merging arrays with spreading:

Spreading can also be used with objects

const originalObject = {
  name: 'John',
  isFootballFan: true,
  club: 'Chelsea',
};

// clone with Object.assign()
const clonedObject1 = Object.assign({}, originalObject),
  // clone with spread operator
  clonedObject2 = { ...originalObject };

Deep cloning

const originalObject = {
  name: 'John',
  isFootballFan: true,
  club: 'Chelsea',
};

// Deep cloning with JSON.stringify() and JSON.parse()
const deepCloned1 = JSON.parse(JSON.stringify(originalObject)),
  // You can also create a deep clone of an object with the `structuredClone()`.
  // `structuredClone()` was added to the JavaScript language in ECMAScript 2019.
  deepCloned2 = structuredClone(originalObject);

Optional chaining

const user = { name: { first: 'John' } };
user.address.house; // TypeError: Cannot read property 'house' of undefined
user.address?.house; // undefined

Ternary operator

const getFee = (isMember) => isMember ? '1 EGP' : '10 EGP';

getFee(true); // "1 EGP"
getFee(false); // "10 EGP"
getFee(null); // "10 EGP"

Weird JavaScript behaviour

let x = 2,
    b = '2';
console.log(x + b); // "22"
console.log(x - b); // 0
console.log(x * b); // 4
console.log(x / b); // 1
console.log(typeof 1); // "number"
console.log(typeof '1'); // "string"
console.log(typeof true); // "boolean"
console.log(typeof undefined); // "undefined"
console.log(typeof null); // "object"
console.log(typeof []); // "object"
console.log(typeof {}); // "object"
console.log(typeof function () {}); // "function"
console.log(typeof (() => {})); // "function"
console.log(typeof NaN); // "number"
console.log(typeof Symbol()); // "symbol"
[1, 2, 3] + '4'; // '1,2,34'
0.1 * 0.2; // 0.020000000000000004
5.3 / 0.1; // 52.99999999999999

https://github.com/denysdovhan/wtfjs

DOM Minpulation

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Selecting DOM Elements

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Ways to query an element in JQuery Vs JS

1. By tag name ex: <p>

myElements = $("p");

JQuery

JavaScript

myElements = document.getElementsByTagName("p");

2. By class name ex: class="intro"

myElements = $(".intro");

JQuery

JavaScript

myElements = document.getElementsByClassName("intro");

Ways to query an element in JQuery Vs JS

3. By id ex: id="id01"

myElement = $("#id01");

JQuery

JavaScript

myElement = document.getElementById("id01");

4. By CSS Selectors ex: class="intro"

myElements = $("p.intro");
//Adjecent sibling selector
myElements = $("p + .intro");
//Direct child selector
myElements = $("p > .intro");

JQuery

JavaScript

myElements = document.querySelectorAll("p.intro");
//Adjecent sibling selector
myElements = document.querySelectorAll("p + .intro");
//Direct child selector
myElements = document.querySelectorAll("p > .intro");

Ways to query an element in JQuery Vs JS

5. Select a Single element

N/A

JQuery

JavaScript

myElement = document.querySelector(".intro");

Add, remove, change Elements

Creating and adding elements to the DOM

1. Create an element

const txt2 = $("<p></p>").text("Text");   // Create with jQuery

JQuery

JavaScript

const txt3 = document.createElement("p");
txt3.innerHTML = "Text";

Creating and adding elements to the DOM

2. Add an element to the DOM

//Inserts content AT THE END of 
//the selected HTML elements. 
$("p").append("Some appended text.");

// Does the same job but in reverse
$("<div />").appendTo("body");

JQuery

JavaScript

const txt3 = document.createElement("p");
txt3.innerHTML = "Text";
//Doesn't return the appended node
Element.append(txt3);
// Returns the appended node,
// Can only append 1 node
const child = Element.appendChild(txt3);

Elmement.insertAdjacentElement("beforeend", txt3);

Element.inserAdjacentHTML("beforeend", string to be parsed);

Creating and adding elements to the DOM

2. Add an element to the DOM

//Inserts content AT THE START of 
//the selected HTML elements. 
$("p").prepend("Some appended text.");

JQuery

JavaScript

const txt3 = document.createElement("p");
txt3.innerHTML = "Text";
//Doesn't return the appended node
Element.prepend(txt3);

Elmement.insertAdjacentElement("afterbegin", txt3);

Element.inserAdjacentHTML("afterbegin", string to be parsed);

Creating and adding elements to the DOM

2. Add an element to the DOM

//Inserts content BEFORE of 
//the selected HTML elements. 
$("img").before("Some text after");

JQuery

JavaScript

Elmement.insertAdjacentElement("beforebegin", txt3);

Element.inserAdjacentHTML("beforebegin", string to be parsed);

Creating and adding elements to the DOM

2. Add an element to the DOM

//Inserts content AFTER of 
//the selected HTML elements. 
$("img").after("Some text after");

JQuery

JavaScript

Elmement.insertAdjacentElement("afterend", txt3);

Element.inserAdjacentHTML("afterend", string to be parsed);

Creating and adding elements to the DOM

3. Replace an element in the DOM

//Accepts multiply Strings, nodes 
$("div.second").replaceWith("<h2>New heading</h2>");

JQuery

JavaScript

//Accepts multiply strings or nodes
p.replaceWith(span);

Creating and adding elements to the DOM

4. remove an element from the DOM

$("#div1").remove();

JQuery

JavaScript

document.querySelector("#div1").remove();

Add, remove and toggle class name

1. Add a class name to an element

//Adds one or more class names 
$("p").addClass("intro");

JQuery

JavaScript

//Adds one or more class names
div.classList.add("intro");

2. Remove class name from an element

//Removes one or more class names 
$("p").removeClass("intro");

JQuery

JavaScript

//Removes one or more class names
div.classList.remove("intro");

Add, remove and toggle class name

3. Replace a class name in an element

//replace one class name 
$('.blue').removeClass('oldClass').addClass('newClass');

JQuery

JavaScript

//replaces one class name with another one
//returns a boolean 
div.classList.replace("oldClass", "newClass");

Add, remove and toggle class name

4. Toggle a class name in an element

//toggle one or more classes 
$("p").toggleClass("main");

JQuery

JavaScript

//adds or removes a class
//returns a boolean 
div.classList.toggle("main");

Animating Elements

1. requestAnimationFrame

N/A

JQuery

JavaScript

const requestID = window.requestAnimationFrame(callback);

//Request Cancelation
window.cancelAnimationFrame(requestID);

Example: https://codepen.io/chriscoyier/pen/DEWGWp

Animating Elements

2. Animate

//By default, all HTML elements have a static position, and cannot be moved.
//To manipulate the position, remember to first set the CSS position property of the element 
//to relative, fixed, or absolute!
$("div").animate({left: '250px'}, 1000, callback);

JQuery

JavaScript

Element.animate(keyframes, options)

// keyframes: Either an array of keyframe objects, 
// or a keyframe object whose properties are arrays of values to iterate over.
// 
// options: Either an integer representing the animation's duration (in milliseconds), 
// or an Object containing one or more timing properties and/or options

Example: Element: animate() method - Web APIs | MDN (mozilla.org)

Example: W3Schools Tryit Editor

Events and handling events

1. add Events listeners

$("div").event(callback);
$("div").on("event", callback);

//example:
$("p").click(function(){
 //code
});

$( "#bind" ).on( "click", function() {
  //code
});

JQuery

JavaScript

Element.addEventListener(type, listener, options)

//example:
document.addEventListener("click",(e)=>{
  //code
})

document.onClick = (e)=>{
  //code
};

Events and handling events

2. Remove Events listeners

//Removes all event handlers from the element
$( "p" ).off()

//Removes a click listener 
//foo needs to be the same function that was passed to .on() function
$("body").off( "click", "p", foo );

JQuery

JavaScript

Element.removeEventListener(type, listener, options)

//example: foo needs to be the same function
//that was passed to addEventListener
document.removeEventListener("click", foo)

//Remove all listeners
elem.replaceWith(elem.cloneNode(true));

Form validation

This type of validation involves checking all the mandatory fields and making sure they're properly filled in.

A Pen by ahmed-fatahallah (codepen.io)

1. Basic Validation

Form validation

This type of validation actually looks at the values in the form and verifies that they are correct.

Validating email addresses is notoriously difficult – there are a vast number of legitimate email addresses and hosts, and it's impossible to guess all the valid combinations of characters.

That said, there are a few key factors that are common in all valid email addresses:

  • An address must contain one @ and at least one dot (.) character
  • The @ character cannot be the first character in the address
  • The . must come at least one character after the @ character

A Pen by ahmed-fatahallah (codepen.io)

2. Data Format Validation

Referrences

  1. MDN Web Docs (mozilla.org)
  2. jQuery API Documentation
  3. jQuery Tutorial (w3schools.com)
  4. Basic Form Validation in JavaScript (freecodecamp.org)
  5. Stack Overflow - Where Developers Learn, Share, & Build Careers

Selecting Elements

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Selecting Elements

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