<!DOCTYPE html>
<html>
  <head>
    <title>30DaysOfScript:Inline Script</title>
  </head>
  <body>
    <button onclick="alert('Welcome to 30DaysOfJavaScript!')">Click Me</button>
  </body>
</html>

<!DOCTYPE html>
<html>
  <head>
    <title>30DaysOfScript:Internal Script</title>
    <script>
      console.log('Welcome to 30DaysOfJavaScript')
    </script>
  </head>
  <body></body>
</html>

<!DOCTYPE html>
<html>
  <head>
    <title>30DaysOfScript:Internal Script</title>
  </head>
  <body>
    <button onclick="alert('Welcome to 30DaysOfJavaScript!');">Click Me</button>
    <script>
      console.log('Welcome to 30DaysOfJavaScript')
    </script>
  </body>
</html>

console.log('Welcome to 30DaysOfJavaScript')

<!DOCTYPE html>
<html>
  <head>
    <title>30DaysOfJavaScript:External script</title>
    <script src="introduction.js"></script>
  </head>
  <body></body>
</html>

<!DOCTYPE html>
<html>
  <head>
    <title>30DaysOfJavaScript:External script</title>
  </head>
  <body>
    //it could be in the header or in the body // Here is the recommended place
    to put the external script
    <script src="introduction.js"></script>
  </body>
</html>

console.log('Hello, World!')

<!DOCTYPE html>
<html>
  <head>
    <title>Multiple External Scripts</title>
  </head>
  <body>
    <script src="./helloworld.js"></script>
    <script src="./introduction.js"></script>
  </body>
</html>

let firstName = 'Asabeneh'
firstName = 'Eyob'

const PI = 3.14 // Not allowed to reassign PI to a new value
// PI = 3.

// syntax
const arr = Array()
// or
// let arr = new Array()
console.log(arr) // []

// syntax
// This the most recommended way to create an empty list
const arr = []
console.log(arr)

const numbers = [0, 3.14, 9.81, 37, 98.6, 100] // array of numbers
const fruits = ['banana', 'orange', 'mango', 'lemon'] // array of strings, fruits
const vegetables = ['Tomato', 'Potato', 'Cabbage', 'Onion', 'Carrot'] // array of strings, vegetables
const animalProducts = ['milk', 'meat', 'butter', 'yoghurt'] // array of strings, products
const webTechs = ['HTML', 'CSS', 'JS', 'React', 'Redux', 'Node', 'MongDB'] // array of web technologies
const countries = ['Finland', 'Denmark', 'Sweden', 'Norway', 'Iceland'] // array of strings, countries

// Print the array and its length

console.log('Numbers:', numbers)
console.log('Number of numbers:', numbers.length)

console.log('Fruits:', fruits)
console.log('Number of fruits:', fruits.length)

console.log('Vegetables:', vegetables)
console.log('Number of vegetables:', vegetables.length)

console.log('Animal products:', animalProducts)
console.log('Number of animal products:', animalProducts.length)

console.log('Web technologies:', webTechs)
console.log('Number of web technologies:', webTechs.length)

console.log('Countries:', countries)
console.log('Number of countries:', countries.length)

Numbers: [0, 3.14, 9.81, 37, 98.6, 100]
Number of numbers: 6
Fruits: ['banana', 'orange', 'mango', 'lemon']
Number of fruits: 4
Vegetables: ['Tomato', 'Potato', 'Cabbage', 'Onion', 'Carrot']
Number of vegetables: 5
Animal products: ['milk', 'meat', 'butter', 'yoghurt']
Number of animal products: 4
Web technologies: ['HTML', 'CSS', 'JS', 'React', 'Redux', 'Node', 'MongDB']
Number of web technologies: 7
Countries: ['Finland', 'Estonia', 'Denmark', 'Sweden', 'Norway']
Number of countries: 5

const arr = [
  'Asabeneh',
  250,
  true,
  { country: 'Finland', city: 'Helsinki' },
  { skills: ['HTML', 'CSS', 'JS', 'React', 'Python'] },
] // arr containing different data types
console.log(arr)

let js = 'JavaScript'
const charsInJavaScript = js.split('')

console.log(charsInJavaScript) // ["J", "a", "v", "a", "S", "c", "r", "i", "p", "t"]

let companiesString = 'Facebook, Google, Microsoft, Apple, IBM, Oracle, Amazon'
const companies = companiesString.split(',')

console.log(companies) // ["Facebook", " Google", " Microsoft", " Apple", " IBM", " Oracle", " Amazon"]
let txt =
  'I love teaching and empowering people. I teach HTML, CSS, JS, React, Python.'
const words = txt.split(' ')

console.log(words)
// the text has special characters think how you can just get only the words
// ["I", "love", "teaching", "and", "empowering", "people.", "I", "teach", "HTML,", "CSS,", "JS,", "React,", "Python"]

const fruits = ['banana', 'orange', 'mango', 'lemon']
let firstFruit = fruits[0] // we are accessing the first item using its index

console.log(firstFruit) // banana

secondFruit = fruits[1]
console.log(secondFruit) // orange

let lastFruit = fruits[3]
console.log(lastFruit) // lemon
// Last index can be calculated as follows

let lastIndex = fruits.length - 1
lastFruit = fruits[lastIndex]

console.log(lastFruit) // lemon

const numbers = [0, 3.14, 9.81, 37, 98.6, 100] // set of numbers

console.log(numbers.length) // => to know the size of the array, which is 6
console.log(numbers) // -> [0, 3.14, 9.81, 37, 98.6, 100]
console.log(numbers[0]) //  -> 0
console.log(numbers[5]) //  -> 100

let lastIndex = numbers.length - 1
console.log(numbers[lastIndex]) // -> 100

const webTechs = [
  'HTML',
  'CSS',
  'JavaScript',
  'React',
  'Redux',
  'Node',
  'MongoDB',
] // List of web technologies

console.log(webTechs) // all the array items
console.log(webTechs.length) // => to know the size of the array, which is 7
console.log(webTechs[0]) //  -> HTML
console.log(webTechs[6]) //  -> MongoDB

let lastIndex = webTechs.length - 1
console.log(webTechs[lastIndex]) // -> MongoDB

const countries = [
  'Albania',
  'Bolivia',
  'Canada',
  'Denmark',
  'Ethiopia',
  'Finland',
  'Germany',
  'Hungary',
  'Ireland',
  'Japan',
  'Kenya',
] // List of countries

console.log(countries) // -> all countries in array
console.log(countries[0]) //  -> Albania
console.log(countries[10]) //  -> Kenya

let lastIndex = countries.length - 1
console.log(countries[lastIndex]) //  -> Kenya

const shoppingCart = [
  'Milk',
  'Mango',
  'Tomato',
  'Potato',
  'Avocado',
  'Meat',
  'Eggs',
  'Sugar',
] // List of food products

console.log(shoppingCart) // -> all shoppingCart in array
console.log(shoppingCart[0]) //  -> Milk
console.log(shoppingCart[7]) //  -> Sugar

let lastIndex = shoppingCart.length - 1
console.log(shoppingCart[lastIndex]) //  -> Sugar

const numbers = [1, 2, 3, 4, 5]
numbers[0] = 10 // changing 1 at index 0 to 10
numbers[1] = 20 // changing  2 at index 1 to 20

console.log(numbers) // [10, 20, 3, 4, 5]

const countries = [
  'Albania',
  'Bolivia',
  'Canada',
  'Denmark',
  'Ethiopia',
  'Finland',
  'Germany',
  'Hungary',
  'Ireland',
  'Japan',
  'Kenya',
]

countries[0] = 'Afghanistan' // Replacing Albania by Afghanistan
let lastIndex = countries.length - 1
countries[lastIndex] = 'Korea' // Replacing Kenya by Korea

console.log(countries)

["Afghanistan", "Bolivia", "Canada", "Denmark", "Ethiopia", "Finland", "Germany", "Hungary", "Ireland", "Japan", "Korea"]

const arr = Array() // creates an an empty array
console.log(arr)

const eightEmptyValues = Array(8) // it creates eight empty values
console.log(eightEmptyValues) // [empty x 8]

const arr = Array() // creates an an empty array
console.log(arr)

const eightXvalues = Array(8).fill('X') // it creates eight element values filled with 'X'
console.log(eightXvalues) // ['X', 'X','X','X','X','X','X','X']

const eight0values = Array(8).fill(0) // it creates eight element values filled with '0'
console.log(eight0values) // [0, 0, 0, 0, 0, 0, 0, 0]

const four4values = Array(4).fill(4) // it creates 4 element values filled with '4'
console.log(four4values) // [4, 4, 4, 4]

const firstList = [1, 2, 3]
const secondList = [4, 5, 6]
const thirdList = firstList.concat(secondList)

console.log(thirdList) // [1, 2, 3, 4, 5, 6]

const fruits = ['banana', 'orange', 'mango', 'lemon'] // array of fruits
const vegetables = ['Tomato', 'Potato', 'Cabbage', 'Onion', 'Carrot'] // array of vegetables
const fruitsAndVegetables = fruits.concat(vegetables) // concatenate the two arrays

console.log(fruitsAndVegetables)

["banana", "orange", "mango", "lemon", "Tomato", "Potato", "Cabbage", "Onion", "Carrot"]

const numbers = [1, 2, 3, 4, 5]
console.log(numbers.length) // -> 5 is the size of the array

const numbers = [1, 2, 3, 4, 5]

console.log(numbers.indexOf(5)) // -> 4
console.log(numbers.indexOf(0)) // -> -1
console.log(numbers.indexOf(1)) // -> 0
console.log(numbers.indexOf(6)) // -> -1

// let us check if a banana exist in the array

const fruits = ['banana', 'orange', 'mango', 'lemon']
let index = fruits.indexOf('banana') // 0

if (index != -1) {
  console.log('This fruit does exist in the array')
} else {
  console.log('This fruit does not exist in the array')
}
// This fruit does exist in the array

// we can use also ternary here
index != -1
  ? console.log('This fruit does exist in the array')
  : console.log('This fruit does not exist in the array')

// let us check if a avocado exist in the array
let indexOfAvocado = fruits.indexOf('avocado') // -1, if the element not found index is -1
if (indexOfAvocado != -1) {
  console.log('This fruit does exist in the array')
} else {
  console.log('This fruit does not exist in the array')
}
// This fruit does not exist in the array

const numbers = [1, 2, 3, 4, 5, 3, 1, 2]

console.log(numbers.lastIndexOf(2)) // 7
console.log(numbers.lastIndexOf(0)) // -1
console.log(numbers.lastIndexOf(1)) //  6
console.log(numbers.lastIndexOf(4)) //  3
console.log(numbers.lastIndexOf(6)) // -1

const numbers = [1, 2, 3, 4, 5]

console.log(numbers.includes(5)) // true
console.log(numbers.includes(0)) // false
console.log(numbers.includes(1)) // true
console.log(numbers.includes(6)) // false

const webTechs = [
  'HTML',
  'CSS',
  'JavaScript',
  'React',
  'Redux',
  'Node',
  'MongoDB',
] // List of web technologies

console.log(webTechs.includes('Node')) // true
console.log(webTechs.includes('C')) // false

const numbers = [1, 2, 3, 4, 5]
console.log(Array.isArray(numbers)) // true

const number = 100
console.log(Array.isArray(number)) // false

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

const names = ['Asabeneh', 'Mathias', 'Elias', 'Brook']
console.log(names.toString()) // Asabeneh,Mathias,Elias,Brook

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

const names = ['Asabeneh', 'Mathias', 'Elias', 'Brook']

console.log(names.join()) // Asabeneh,Mathias,Elias,Brook
console.log(names.join('')) //AsabenehMathiasEliasBrook
console.log(names.join(' ')) //Asabeneh Mathias Elias Brook
console.log(names.join(', ')) //Asabeneh, Mathias, Elias, Brook
console.log(names.join(' # ')) //Asabeneh # Mathias # Elias # Brook

const webTechs = [
  'HTML',
  'CSS',
  'JavaScript',
  'React',
  'Redux',
  'Node',
  'MongoDB',
] // List of web technologies

console.log(webTechs.join()) // "HTML,CSS,JavaScript,React,Redux,Node,MongoDB"
console.log(webTechs.join(' # ')) // "HTML # CSS # JavaScript # React # Redux # Node # MongoDB"

const numbers = [1, 2, 3, 4, 5]

console.log(numbers.slice()) // -> it copies all  item
console.log(numbers.slice(0)) // -> it copies all  item
console.log(numbers.slice(0, numbers.length)) // it copies all  item
console.log(numbers.slice(1, 4)) // -> [2,3,4] // it doesn't include the ending position

const numbers = [1, 2, 3, 4, 5]

console.log(numbers.splice()) // -> remove all items

const numbers = [1, 2, 3, 4, 5]
console.log(numbers.splice(0, 1)) // remove the first item

const numbers = [1, 2, 3, 4, 5, 6]
console.log(numbers.splice(3, 3, 7, 8, 9)) // -> [1, 2, 3, 7, 8, 9] //it removes three item and replace three items

// syntax
const arr = ['item1', 'item2', 'item3']
arr.push('new item')

console.log(arr)
// ['item1', 'item2','item3','new item']

const numbers = [1, 2, 3, 4, 5]
numbers.push(6)

console.log(numbers) // -> [1,2,3,4,5,6]

numbers.pop() // -> remove one item from the end
console.log(numbers) // -> [1,2,3,4,5]

let fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.push('apple')

console.log(fruits) // ['banana', 'orange', 'mango', 'lemon', 'apple']

fruits.push('lime')
console.log(fruits) // ['banana', 'orange', 'mango', 'lemon', 'apple', 'lime']

const numbers = [1, 2, 3, 4, 5]
numbers.pop() // -> remove one item from the end

console.log(numbers) // -> [1,2,3,4]

const numbers = [1, 2, 3, 4, 5]
numbers.shift() // -> remove one item from the beginning

console.log(numbers) // -> [2,3,4,5]

const numbers = [1, 2, 3, 4, 5]
numbers.unshift(0) // -> add one item from the beginning

console.log(numbers) // -> [0,1,2,3,4,5]

const numbers = [1, 2, 3, 4, 5]
numbers.reverse() // -> reverse array order

console.log(numbers) // [5, 4, 3, 2, 1]

numbers.reverse()
console.log(numbers) // [1, 2, 3, 4, 5]

const webTechs = [
  'HTML',
  'CSS',
  'JavaScript',
  'React',
  'Redux',
  'Node',
  'MongoDB',
]

webTechs.sort()
console.log(webTechs) // ["CSS", "HTML", "JavaScript", "MongoDB", "Node", "React", "Redux"]

webTechs.reverse() // after sorting we can reverse it
console.log(webTechs) // ["Redux", "React", "Node", "MongoDB", "JavaScript", "HTML", "CSS"]

const firstNums = [1, 2, 3]
const secondNums = [1, 4, 9]

const arrayOfArray = [
  [1, 2, 3],
  [1, 2, 3],
]
console.log(arrayOfArray[0]) // [1, 2, 3]

const frontEnd = ['HTML', 'CSS', 'JS', 'React', 'Redux']
const backEnd = ['Node', 'Express', 'MongoDB']
const fullStack = [frontEnd, backEnd]
console.log(fullStack) // [["HTML", "CSS", "JS", "React", "Redux"], ["Node", "Express", "MongoDB"]]
console.log(fullStack.length) // 2
console.log(fullStack[0]) // ["HTML", "CSS", "JS", "React", "Redux"]
console.log(fullStack[1]) // ["Node", "Express", "MongoDB"]

const countries = [
  'Albania',
  'Bolivia',
  'Canada',
  'Denmark',
  'Ethiopia',
  'Finland',
  'Germany',
  'Hungary',
  'Ireland',
  'Japan',
  'Kenya',
]

const webTechs = [
  'HTML',
  'CSS',
  'JavaScript',
  'React',
  'Redux',
  'Node',
  'MongoDB',
]

// syntax
if (condition) {
  //this part of code runs for truthy condition
}

let num = 3
if (num > 0) {
  console.log(`${num} is a positive number`)
}
//  3 is a positive number

let isRaining = true
if (isRaining) {
  console.log('Remember to take your rain coat.')
}

// syntax
if (condition) {
  // this part of code runs for truthy condition
} else {
  // this part of code runs for false condition
}

let num = 3
if (num > 0) {
  console.log(`${num} is a positive number`)
} else {
  console.log(`${num} is a negative number`)
}
//  3 is a positive number

num = -3
if (num > 0) {
  console.log(`${num} is a positive number`)
} else {
  console.log(`${num} is a negative number`)
}
//  -3 is a negative number

let isRaining = true
if (isRaining) {
  console.log('You need a rain coat.')
} else {
  console.log('No need for a rain coat.')
}
// You need a rain coat.

isRaining = false
if (isRaining) {
  console.log('You need a rain coat.')
} else {
  console.log('No need for a rain coat.')
}
// No need for a rain coat.

// syntax
if (condition) {
  // code
} else if (condition) {
  // code
} else {
  //  code
}

let a = 0
if (a > 0) {
  console.log(`${a} is a positive number`)
} else if (a < 0) {
  console.log(`${a} is a negative number`)
} else if (a == 0) {
  console.log(`${a} is zero`)
} else {
  console.log(`${a} is not a number`)
}

// if else if else
let weather = 'sunny'
if (weather === 'rainy') {
  console.log('You need a rain coat.')
} else if (weather === 'cloudy') {
  console.log('It might be cold, you need a jacket.')
} else if (weather === 'sunny') {
  console.log('Go out freely.')
} else {
  console.log('No need for rain coat.')
}

switch (caseValue) {
  case 1:
    // code
    break
  case 2:
    // code
    break
  case 3:
  // code
  default:
  // code
}

let weather = 'cloudy'
switch (weather) {
  case 'rainy':
    console.log('You need a rain coat.')
    break
  case 'cloudy':
    console.log('It might be cold, you need a jacket.')
    break
  case 'sunny':
    console.log('Go out freely.')
    break
  default:
    console.log(' No need for rain coat.')
}

// Switch More Examples
let dayUserInput = prompt('What day is today ?')
let day = dayUserInput.toLowerCase()

switch (day) {
  case 'monday':
    console.log('Today is Monday')
    break
  case 'tuesday':
    console.log('Today is Tuesday')
    break
  case 'wednesday':
    console.log('Today is Wednesday')
    break
  case 'thursday':
    console.log('Today is Thursday')
    break
  case 'friday':
    console.log('Today is Friday')
    break
  case 'saturday':
    console.log('Today is Saturday')
    break
  case 'sunday':
    console.log('Today is Sunday')
    break
  default:
    console.log('It is not a week day.')
}

let num = prompt('Enter number')
switch (true) {
  case num > 0:
    console.log('Number is positive')
    break
  case num == 0:
    console.log('Numbers is zero')
    break
  case num < 0:
    console.log('Number is negative')
    break
  default:
    console.log('Entered value was not a number')
}

let isRaining = true
isRaining
  ? console.log('You need a rain coat.')
  : console.log('No need for a rain coat.')

    What is the day  today? Saturday
    Saturday is a weekend.

    What is the day today? saturDaY
    Saturday is a weekend.

    What is the day today? Friday
    Friday is a working day.

    What is the day today? FrIDAy
    Friday is a working day.

  Enter a month: January
  January has 31 days.

  Enter a month: JANUARY
  January has 31 day

  Enter a month: February
  February has 28 days.

  Enter a month: FEbruary
  February has 28 days.

// for loop syntax

for (initialization, condition, increment/decrement) {
    code goes here
}

for (let i = 0; i < 6; i++) {
  console.log(i)
}

let sum = 0
for (let i = 0; i < 101; i++) {
  sum += i
}

console.log(sum)

let sum = 0
for (let i = 0; i < 101; i += 2) {
  sum += i
}

console.log(sum)

// or another way

let total = 0
for (let i = 0; i < 101; i++) {
  if (i % 2 == 0) {
    total += i
  }
}
console.log(total)

const nums = [1, 2, 3, 4, 5]
for (let i = 0; i < 6; i++) {
  console.log(nums[i])
}

for (let i = 5; i >= 0; i--) {
  console.log(i)
}

const nums = [1, 2, 3, 4, 5]
const lastIndex = nums.length - 1
const newArray = []
for (let i = lastIndex; i >= 0; i--) {
  newArray.push(nums[i])
}

console.log(newArray)

let count = prompt('Enter a positive number: ')
while (count > 0) {
  console.log(count)
  count--
}

let count = 0
do {
  console.log(count)
  count++
} while (count < 11)

let count = 11
do {
  console.log(count)
  count++
} while (count < 11)

const numbers = [1, 2, 3, 4, 5]
for (const number of numbers) {
  console.log(number)
}

const countries = ['Finland', 'Sweden', 'Norway', 'Denmark', 'Iceland']
for (const country of countries) {
  console.log(country.toUpperCase())
}

const numbers = [1, 2, 3, 4, 5]
numbers.forEach((number, i) => {
  console.log(number, i)
})

const countries = ['Finland', 'Sweden', 'Norway', 'Denmark', 'Iceland']
countries.forEach((country, i, arr) => {
  console.log(i, country.toUpperCase())
})

const user = {
  firstName: 'Asabeneh',
  lastName: 'Yetayeh',
  age: 250,
  country: 'Finland',
  skills: ['HTML', 'CSS', 'JS', 'React', 'Node', 'Python', 'D3.js'],
}

for (const key in user) {
  console.log(key, user[key])
}

for (let i = 0; i <= 5; i++) {
  if (i == 3) {
    break
  }
  console.log(i)
}

// 0 1 2

for (let i = 0; i <= 5; i++) {
  if (i == 3) {
    continue
  }
  console.log(i)
}
// 0 1 2 4 5

//scope.js
a = 'JavaScript' // is a window scope this found anywhere
b = 10 // this is a window scope variable
function letsLearnScope() {
  console.log(a, b)
  if (true) {
    console.log(a, b)
  }
}
console.log(a, b) // accessible

//scope.js
let a = 'JavaScript' // is a global scope it will be found anywhere in this file
let b = 10 // is a global scope it will be found anywhere in this file
function letsLearnScope() {
  console.log(a, b) // JavaScript 10, accessible
  if (true) {
    let a = 'Python'
    let b = 100
    console.log(a, b) // Python 100
  }
  console.log(a, b)
}
letsLearnScope()
console.log(a, b) // JavaScript 10, accessible

//scope.js
let a = 'JavaScript' // is a global scope it will be found anywhere in this file
let b = 10 // is a global scope it will be found anywhere in this file
function letsLearnScope() {
  console.log(a, b) // JavaScript 10, accessible
  let c = 30
  if (true) {
    // we can access from the function and outside the function but
    // variables declared inside the if will not be accessed outside the if block
    let a = 'Python'
    let b = 20
    let d = 40
    console.log(a, b, c) // Python 20 30
  }
  // we can not access c because c's scope is only the if block
  console.log(a, b) // JavaScript 10
}
letsLearnScope()
console.log(a, b) // JavaScript 10, accessible

//scope.js
function letsLearnScope() {
  var gravity = 9.81
  console.log(gravity)
}
// console.log(gravity), Uncaught ReferenceError: gravity is not defined

if (true) {
  var gravity = 9.81
  console.log(gravity) // 9.81
}
console.log(gravity) // 9.81

for (var i = 0; i < 3; i++) {
  console.log(i) // 1, 2, 3
}
console.log(i)

//scope.js
function letsLearnScope() {
  // you can use let or const, but gravity is constant I prefer to use const
  const gravity = 9.81
  console.log(gravity)
}
// console.log(gravity), Uncaught ReferenceError: gravity is not defined

if (true) {
  const gravity = 9.81
  console.log(gravity) // 9.81
}
// console.log(gravity), Uncaught ReferenceError: gravity is not defined

for (let i = 0; i < 3; i++) {
  console.log(i) // 1, 2, 3
}
// console.log(i), Uncaught ReferenceError: gravity is not defined

const person = {}

const rectangle = {
  length: 20,
  width: 20,
}
console.log(rectangle) // {length: 20, width: 20}

const person = {
  firstName: 'Asabeneh',
  lastName: 'Yetayeh',
  age: 250,
  country: 'Finland',
  city: 'Helsinki',
  skills: [
    'HTML',
    'CSS',
    'JavaScript',
    'React',
    'Node',
    'MongoDB',
    'Python',
    'D3.js',
  ],
  isMarried: true,
}
console.log(person)

const person = {
  firstName: 'Asabeneh',
  lastName: 'Yetayeh',
  age: 250,
  country: 'Finland',
  city: 'Helsinki',
  skills: [
    'HTML',
    'CSS',
    'JavaScript',
    'React',
    'Node',
    'MongoDB',
    'Python',
    'D3.js',
  ],
  getFullName: function () {
    return `${this.firstName}${this.lastName}`
  },
  'phone number': '+3584545454545',
}

// accessing values using .
console.log(person.firstName)
console.log(person.lastName)
console.log(person.age)
console.log(person.location)

// value can be accessed using square bracket and key name
console.log(person['firstName'])
console.log(person['lastName'])
console.log(person['age'])
console.log(person['age'])
console.log(person['location'])

// for instance to access the phone number we only use the square bracket method
console.log(person['phone number'])

const person = {
  firstName: 'Asabeneh',
  lastName: 'Yetayeh',
  age: 250,
  country: 'Finland',
  city: 'Helsinki',
  skills: [
    'HTML',
    'CSS',
    'JavaScript',
    'React',
    'Node',
    'MongoDB',
    'Python',
    'D3.js',
  ],
  getFullName: function () {
    return `${this.firstName} ${this.lastName}`
  },
}

console.log(person.getFullName())
// Asabeneh Yetayeh

const person = {
  firstName: 'Asabeneh',
  lastName: 'Yetayeh',
  age: 250,
  country: 'Finland',
  city: 'Helsinki',
  skills: [
    'HTML',
    'CSS',
    'JavaScript',
    'React',
    'Node',
    'MongoDB',
    'Python',
    'D3.js',
  ],
  getFullName: function () {
    return `${this.firstName} ${this.lastName}`
  },
}
person.nationality = 'Ethiopian'
person.country = 'Finland'
person.title = 'teacher'
person.skills.push('Meteor')
person.skills.push('SasS')
person.isMarried = true

person.getPersonInfo = function () {
  let skillsWithoutLastSkill = this.skills
    .slice(0, this.skills.length - 1)
    .join(', ')
  let lastSkill = this.skills.slice(this.skills.length - 1)[0]

  let skills = `${skillsWithoutLastSkill}, and ${lastSkill}`
  let fullName = this.getFullName()
  let statement = `${fullName} is a ${this.title}.\nHe lives in ${this.country}.\nHe teaches ${skills}.`
  return statement
}
console.log(person)
console.log(person.getPersonInfo())

Asabeneh Yetayeh is a teacher.
He lives in Finland.
He teaches HTML, CSS, JavaScript, React, Node, MongoDB, Python, D3.js, Meteor, and SasS.

const person = {
  firstName: 'Asabeneh',
  age: 250,
  country: 'Finland',
  city: 'Helsinki',
  skills: ['HTML', 'CSS', 'JS'],
  title: 'teacher',
  address: {
    street: 'Heitamienkatu 16',
    pobox: 2002,
    city: 'Helsinki',
  },
  getPersonInfo: function () {
    return `I am ${this.firstName} and I live in ${this.city}, ${this.country}. I am ${this.age}.`
  },
}

//Object methods: Object.assign, Object.keys, Object.values, Object.entries
//hasOwnProperty

const copyPerson = Object.assign({}, person)
console.log(copyPerson)

const keys = Object.keys(copyPerson)
console.log(keys) //['name', 'age', 'country', 'skills', 'address', 'getPersonInfo']
const address = Object.keys(copyPerson.address)
console.log(address) //['street', 'pobox', 'city']

const values = Object.values(copyPerson)
console.log(values)

const entries = Object.entries(copyPerson)
console.log(entries)

console.log(copyPerson.hasOwnProperty('name'))
console.log(copyPerson.hasOwnProperty('score'))

const users = [
  {
    _id: 'ab12ex',
    username: 'Alex',
    email: 'alex@alex.com',
    password: '123123',
    createdAt: '08/01/2020 9:00 AM',
    isLoggedIn: false,
  },
  {
    _id: 'fg12cy',
    username: 'Asab',
    email: 'asab@asab.com',
    password: '123456',
    createdAt: '08/01/2020 9:30 AM',
    isLoggedIn: true,
  },
  {
    _id: 'zwf8md',
    username: 'Brook',
    email: 'brook@brook.com',
    password: '123111',
    createdAt: '08/01/2020 9:45 AM',
    isLoggedIn: true,
  },
  {
    _id: 'eefamr',
    username: 'Martha',
    email: 'martha@martha.com',
    password: '123222',
    createdAt: '08/01/2020 9:50 AM',
    isLoggedIn: false,
  },
  {
    _id: 'ghderc',
    username: 'Thomas',
    email: 'thomas@thomas.com',
    password: '123333',
    createdAt: '08/01/2020 10:00 AM',
    isLoggedIn: false,
  },
]

const products = [
  {
    _id: 'eedfcf',
    name: 'mobile phone',
    description: 'Huawei Honor',
    price: 200,
    ratings: [
      { userId: 'fg12cy', rate: 5 },
      { userId: 'zwf8md', rate: 4.5 },
    ],
    likes: [],
  },
  {
    _id: 'aegfal',
    name: 'Laptop',
    description: 'MacPro: System Darwin',
    price: 2500,
    ratings: [],
    likes: ['fg12cy'],
  },
  {
    _id: 'hedfcg',
    name: 'TV',
    description: 'Smart TV:Procaster',
    price: 400,
    ratings: [{ userId: 'fg12cy', rate: 5 }],
    likes: ['fg12cy'],
  },
]

//declaring a function without a parameter
function functionName() {
  // code goes here
}
functionName() // calling function by its name and with parentheses

// function without parameter,  a function which make a number square
function square() {
  let num = 2
  let sq = num * num
  console.log(sq)
}

square() // 4

// function without parameter
function addTwoNumbers() {
  let numOne = 10
  let numTwo = 20
  let sum = numOne + numTwo

  console.log(sum)
}

addTwoNumbers() // a function has to be called by its name to be executed

function printFullName() {
  let firstName = 'Asabeneh'
  let lastName = 'Yetayeh'
  let space = ' '
  let fullName = firstName + space + lastName
  console.log(fullName)
}

printFullName() // calling a function

function printFullName() {
  let firstName = 'Asabeneh'
  let lastName = 'Yetayeh'
  let space = ' '
  let fullName = firstName + space + lastName
  return fullName
}
console.log(printFullName())

function addTwoNumbers() {
  let numOne = 2
  let numTwo = 3
  let total = numOne + numTwo
  return total
}

console.log(addTwoNumbers())

// function with one parameter
function functionName(parm1) {
  //code goes her
}
functionName(parm1) // during calling or invoking one argument needed

function areaOfCircle(r) {
  let area = Math.PI * r * r
  return area
}

console.log(areaOfCircle(10)) // should be called with one argument

function square(number) {
  return number * number
}

console.log(square(10))

// function with two parameters
function functionName(parm1, parm2) {
  //code goes her
}
functionName(parm1, parm2) // during calling or invoking two arguments needed
// Function without parameter doesn't take input, so lets make a function with parameters
function sumTwoNumbers(numOne, numTwo) {
  let sum = numOne + numTwo
  console.log(sum)
}
sumTwoNumbers(10, 20) // calling functions
// If a function doesn't return it doesn't store data, so it should return

function sumTwoNumbers(numOne, numTwo) {
  let sum = numOne + numTwo
  return sum
}

console.log(sumTwoNumbers(10, 20))
function printFullName(firstName, lastName) {
  return `${firstName} ${lastName}`
}
console.log(printFullName('Asabeneh', 'Yetayeh'))

// function with multiple parameters
function functionName(parm1, parm2, parm3,...){
  //code goes here
}
functionName(parm1,parm2,parm3,...) // during calling or invoking three arguments needed


// this function takes array as a parameter and sum up the numbers in the array
function sumArrayValues(arr) {
  let sum = 0;
  for (let i = 0; i < arr.length; i++) {
    sum = sum + arr[i];
  }
  return sum;
}
const numbers = [1, 2, 3, 4, 5];
    //calling a function
console.log(sumArrayValues(numbers));


    const areaOfCircle = (radius) => {
      let area = Math.PI * radius * radius;
      return area;
    }
console.log(areaOfCircle(10))

// Let us access the arguments object
​
function sumAllNums() {
 console.log(arguments)
}

sumAllNums(1, 2, 3, 4))
// Arguments(4) [1, 2, 3, 4, callee: ƒ, Symbol(Symbol.iterator): ƒ]

// function declaration
​
function sumAllNums() {
  let sum = 0
  for (let i = 0; i < arguments.length; i++) {
    sum += arguments[i]
  }
  return sum
}

console.log(sumAllNums(1, 2, 3, 4)) // 10
console.log(sumAllNums(10, 20, 13, 40, 10))  // 93
console.log(sumAllNums(15, 20, 30, 25, 10, 33, 40))  // 173

// Let us access the arguments object
​
const sumAllNums = (...args) => {
 // console.log(arguments), arguments object not found in arrow function
 // instead we use an a parameter followed by spread operator
 console.log(args)
}

sumAllNums(1, 2, 3, 4))
// [1, 2, 3, 4]

// function declaration
​
const sumAllNums = (...args) => {
  let sum = 0
  for (const element of args) {
    sum += element
  }
  return sum
}

console.log(sumAllNums(1, 2, 3, 4)) // 10
console.log(sumAllNums(10, 20, 13, 40, 10))  // 93
console.log(sumAllNums(15, 20, 30, 25, 10, 33, 40))  // 173

const anonymousFun = function () {
  console.log(
    'I am an anonymous function and my value is stored in anonymousFun'
  )
}

// Function expression
const square = function (n) {
  return n * n
}

console.log(square(2)) // -> 4

;(function (n) {
  console.log(n * n)
})(2) // 4, but instead of just printing if we want to return and store the data, we do as shown below

let squaredNum = (function (n) {
  return n * n
})(10)

console.log(squaredNum)

// This is how we write normal or declaration function
// Let us change this declaration function to an arrow function
function square(n) {
  return n * n
}

console.log(square(2)) // 4

const square = (n) => {
  return n * n
}

console.log(square(2)) // -> 4

// if we have only one line in the code block, it can be written as follows, explicit return
const square = (n) => n * n // -> 4

const changeToUpperCase = (arr) => {
  const newArr = []
  for (const element of arr) {
    newArr.push(element.toUpperCase())
  }
  return newArr
}

const countries = ['Finland', 'Sweden', 'Norway', 'Denmark', 'Iceland']
console.log(changeToUpperCase(countries))

// ["FINLAND", "SWEDEN", "NORWAY", "DENMARK", "ICELAND"]

const printFullName = (firstName, lastName) => {
  return `${firstName} ${lastName}`
}

console.log(printFullName('Asabeneh', 'Yetayeh'))

const printFullName = (firstName, lastName) => `${firstName} ${lastName}`

console.log(printFullName('Asabeneh', 'Yetayeh'))

// syntax
// Declaring a function
function functionName(param = value) {
  //codes
}

// Calling function
functionName()
functionName(arg)

function greetings(name = 'Peter') {
  let message = `${name}, welcome to 30 Days Of JavaScript!`
  return message
}

console.log(greetings())
console.log(greetings('Asabeneh'))

function generateFullName(firstName = 'Asabeneh', lastName = 'Yetayeh') {
  let space = ' '
  let fullName = firstName + space + lastName
  return fullName
}

console.log(generateFullName())
console.log(generateFullName('David', 'Smith'))

function calculateAge(birthYear, currentYear = 2019) {
  let age = currentYear - birthYear
  return age
}

console.log('Age: ', calculateAge(1819))

function weightOfObject(mass, gravity = 9.81) {
  let weight = mass * gravity + ' N' // the value has to be changed to string first
  return weight
}

console.log('Weight of an object in Newton: ', weightOfObject(100)) // 9.81 gravity at the surface of Earth
console.log('Weight of an object in Newton: ', weightOfObject(100, 1.62)) // gravity at surface of Moon

// syntax
// Declaring a function
const functionName = (param = value) => {
  //codes
}

// Calling function
functionName()
functionName(arg)

const greetings = (name = 'Peter') => {
  let message = name + ', welcome to 30 Days Of JavaScript!'
  return message
}

console.log(greetings())
console.log(greetings('Asabeneh'))

const generateFullName = (firstName = 'Asabeneh', lastName = 'Yetayeh') => {
  let space = ' '
  let fullName = firstName + space + lastName
  return fullName
}

console.log(generateFullName())
console.log(generateFullName('David', 'Smith'))

const calculateAge = (birthYear, currentYear = 2019) => currentYear - birthYear
console.log('Age: ', calculateAge(1819))

const weightOfObject = (mass, gravity = 9.81) => mass * gravity + ' N'

console.log('Weight of an object in Newton: ', weightOfObject(100)) // 9.81 gravity at the surface of Earth
console.log('Weight of an object in Newton: ', weightOfObject(100, 1.62)) // gravity at surface of Moon

evensAndOdds(100);
The number of odds are 50.
The number of evens are 51.

sum(1, 2, 3) // -> 6
sum(1, 2, 3, 4) // -> 10

console.log(userIdGenerator());
41XTDbE

// a callback function, the function could be any name
const callback = (n) => {
  return n ** 2
}
​
// function take other function as a callback
function cube(callback, n) {
  return callback(n) * n
}
​
console.log(cube(callback, 3))

// Higher order function returning an other function
const higherOrder = n => {
  const doSomething = m => {
    const doWhatEver = t => {
      return 2 * n + 3 * m + t
    }
    return doWhatEver
  }
​
  return doSomething
}
console.log(higherOrder(2)(3)(10))

const numbers = [1, 2, 3, 4]
const sumArray = arr => {
  let sum = 0
  const callback = function(element) {
    sum += element
  }
  arr.forEach(callback)
  return sum

}
console.log(sumArray(numbers))

10

const numbers = [1, 2, 3, 4]
​
const sumArray = arr => {
  let sum = 0
  arr.forEach(function(element) {
    sum += element
  })
  return sum

}
console.log(sumArray(numbers))

10

// syntax
function callback() {
  // code goes here
}
setInterval(callback, duration)

function sayHello() {
  console.log('Hello')
}
setInterval(sayHello, 2000) // it prints hello in every 2 seconds

// syntax
function callback() {
  // code goes here
}
setTimeout(callback, duration) // duration in milliseconds

function sayHello() {
  console.log('Hello')
}
setTimeout(sayHello, 2000) // it prints hello after it waits for 2 seconds.

const numbers = [1, 2, 3]
const countries = ['Finland', 'Sweden', 'Norway']

for (const number of numbers) {
  console.log(number)
}

for (const country of countries) {
  console.log(country)
}

const numbers = [1, 2, 3]
let num1 = numbers[0]
let num2 = numbers[1]
let num3 = numbers[2]
console.log(num1, num2, num3) // 1, 2, 3

const countries = ['Finland', 'Sweden', 'Norway']
let fin = countries[0]
let swe = countries[1]
let nor = countries[2]
console.log(fin, swe, nor) // Finland, Sweden, Norway

const numbers = [1, 2, 3]
const [num1, num2, num3] = numbers
console.log(num1, num2, num3) // 1, 2, 3,

const constants = [2.72, 3.14, 9.81,37, 100]
const [e, pi, gravity, bodyTemp, boilingTemp] = constants
console.log(e, pi, gravity, bodyTemp, boilingTemp]
// 2.72, 3.14, 9.81, 37,100
const countries = ['Finland', 'Sweden', 'Norway']
const [fin, swe, nor] = countries
console.log(fin, swe, nor) // Finland, Sweden, Norway

const [fin, swe, nor, den] = countries
console.log(den) // undefined

const countries = ['Finland', 'Sweden', undefined, 'Norway']
const [fin, swe, ice = 'Iceland', nor, den = 'Denmark'] = countries
console.log(fin, swe, ice, nor, den) // Finland, Sweden, Iceland, Norway, Denmark

const fullStack = [
  ['HTML', 'CSS', 'JS', 'React'],
  ['Node', 'Express', 'MongoDB']
]

const [frontEnd, backEnd] = fullstack
console.log(frontEnd, backEnd)

//["HTML", "CSS", "JS", "React"] , ["Node", "Express", "MongoDB"]

const fruitsAndVegetables = [['banana', 'orange', 'mango', 'lemon'],  ['Tomato', 'Potato', 'Cabbage', 'Onion', 'Carrot']]

const [fruits, vegetables] = fruitsAndVegetables
console.log(fruits, vegetables]

//['banana', 'orange', 'mango', 'lemon']

//['Tomato', 'Potato', 'Cabbage', 'Onion', 'Carrot']

const countries = ['Finland', 'Sweden', 'Iceland', 'Norway', 'Denmark']
const [fin, , ice, , den] = countries
console.log(fin, ice, den) // Finland, Iceland, Denmark

const nums = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
const [num1, num2, num3, ...rest] = nums
console.log(num1, num2, num3, rest) //1, 2, 3, [4, 5, 6, 7, 8, 9, 10]

const countries = [
  'Germany',
  'France',
  'Belgium',
  'Finland',
  'Sweden',
  'Norway',
  'Denmark',
  'Iceland',
]

let [gem, fra, , ...nordicCountries] = countries
console.log(gem, fra, nordicCountries)
// Germany, France,  ["Finland", "Sweden", "Norway", "Denmark", "Iceland"]

const countries = [
  ['Finland', 'Helsinki'],
  ['Sweden', 'Stockholm'],
  ['Norway', 'Oslo'],
]

for (const [country, city] of countries) {
  console.log(country, city)
}

const fullStack = [
  ['HTML', 'CSS', 'JS', 'React'],
  ['Node', 'Express', 'MongoDB'],
]

for (const [first, second, third, fourth] of fullStack) {
  console.log(first, second, third, fourt)
}

const [x, y] = [2, (value) => value ** 2]

const [count, setCount] = useState(0)

const rectangle = {
  width: 20,
  height: 10,
}

const rectangle = {
  width: 20,
  height: 10,
}

let width = rectangle.width
let height = recangle.height

// or

let width = rectangle[width]
let height = recangle[height]

const rectangle = {
  width: 20,
  height: 10,
}

let { width, height } = rectangle
console.log(width, height, perimeter) // 20, 10

const rectangle = {
  width: 20,
  height: 10,
}

let { width, height, perimeter } = rectangleconsole.log(
  width,
  height,
  perimeter
) // 20, 10, undefined

const rectangle = {
  width: 20,
  height: 10,
}

let { width, height, perimeter = 200 } = rectangle
console.log(width, height, perimeter) // 20, 10, undefined

const rectangle = {
  width: 20,
  height: 10,
}

let { width: w, height: h } = rectangle

const props = {
  user:{
    firstName:'Asabeneh',
    lastName:'Yetayeh',
    age:250
  },
  post:{
    title:'Destructuring and Spread',
    subtitle:'ES6',
    year:2020
},
skills:['JS', 'React', 'Redux', 'Node', 'Python']

}
}

const {user, post, skills} = props
const {firstName, lastName, age} = user
const {title, subtitle, year} = post
const [skillOne, skillTwo, skillThree, skillFour, skillFive] = skills

const props = {
  user:{
    firstName:'Asabeneh',
    lastName:'Yetayeh',
    age:250
  },
  post:{
    title:'Destructuring and Spread',
    subtitle:'ES6',
    year:2020
},
skills:['JS', 'React', 'Redux', 'Node', 'Python']

}

}

const {user:{firstName, lastName, age}, post:{title, subtitle, year}, skills:[skillOne, skillTwo, skillThree, skillFour, skillFive]} = props

const languages = [
  { lang: 'English', count: 91 },
  { lang: 'French', count: 45 },
  { lang: 'Arabic', count: 25 },
  { lang: 'Spanish', count: 24 },
  { lang: 'Russian', count: 9 },
  { lang: 'Portuguese', count: 9 },
  { lang: 'Dutch', count: 8 },
  { lang: 'German', count: 7 },
  { lang: 'Chinese', count: 5 },
  { lang: 'Swahili', count: 4 },
  { lang: 'Serbian', count: 4 },
]

for (const { lang, count } of languages) {
  console.log(`The ${lang} is spoken in ${count} countries.`)
}

const rectangle = { width: 20, height: 10 }
const calcualteArea = ({ width, height }) => width * height
const calculatePerimeter = ({ width, height } = 2 * (width + height))

const person = {
  firstName: 'Asabeneh',
  lastName: 'Yetayeh',
  age: 250,
  country: 'Finland',
  job: 'Instructor and Developer',
  skills: [
    'HTML',
    'CSS',
    'JavaScript',
    'React',
    'Redux',
    'Node',
    'MongoDB',
    'Python',
    'D3.js',
  ],
  languages: ['Amharic', 'English', 'Suomi(Finnish)'],
}

/*
Asabeneh Yetayeh lives in Finland. He is  250 years old. He is an Instructor and Developer. He teaches HTML, CSS, JavaScript, React, Redux, Node, MongoDB, Python and D3.js. He speaks Amharic, English and a little bit of Suomi(Finnish)
*/

const nums = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
let [num1, num2, num3, ...rest] = nums
​
console.log(num1, num2, num3)
console.log(rest)

1 2 3
[4, 5, 6, 7, 8, 9, 10]

const countries = [
  'Germany',
  'France',
  'Belgium',
  'Finland',
  'Sweden',
  'Norway',
  'Denmark',
  'Iceland',
]

let [gem, fra, , ...nordicCountries] = countries

console.log(gem)
console.log(fra)
console.log(nordicCountries)

Germany
France
["Finland", "Sweden", "Norway", "Denmark", "Iceland"]

const evens = [0, 2, 4, 6, 8, 10]
const evenNumbers = [...evens]

const odds = [1, 3, 5, 7, 9]
const oddNumbers = [...odds]

const wholeNumbers = [...evens, ...odds]

console.log(evenNumbers)
console.log(oddNumbers)
console.log(wholeNumbers)

[0, 2, 4, 6, 8, 10]
[1, 3, 5, 7, 9]
[0, 2, 4, 6, 8, 10, 1, 3, 5, 7, 9]

const frontEnd = ['HTML', 'CSS', 'JS', 'React']
const backEnd = ['Node', 'Express', 'MongoDB']
const fullStack = [...frontEnd, ...backEnd]

console.log(fullStack)

["HTML", "CSS", "JS", "React", "Node", "Express", "MongoDB"]

const user = {
  name: 'Asabeneh',
  title: 'Programmer',
  country: 'Finland',
  city: 'Helsinki',
}

const copiedUser = { ...user }
console.log(copiedUser)

{name: "Asabeneh", title: "Programmer", country: "Finland", city: "Helsinki"}

const user = {
  name: 'Asabeneh',
  title: 'Programmer',
  country: 'Finland',
  city: 'Helsinki',
}

const copiedUser = { ...user, title: 'instructor' }
console.log(copiedUser)

{name: "Asabeneh", title: "instructor", country: "Finland", city: "Helsinki"}

const sumAllNums = (...args) => {
  console.log(args)
}

sumAllNums(1, 2, 3, 4, 5)

[1, 2, 3, 4, 5]

const sumAllNums = (...args) => {
  let sum = 0
  for (const num of args) {
    sum += num
  }
  return sum
}

console.log(sumAllNums(1, 2, 3, 4, 5))

15

// syntax in a normal or a function declaration

function callback(item, index, arr) {}
array.forEach(callback)

// or syntax in an arrow function
const callback = (item, i, arr) => {}
array.forEach(callback)

const countries = ['Finland', 'Estonia', 'Sweden', 'Norway']
countries.forEach(function (country, index, arr) {
  console.log(i, country.toUpperCase())
})

const countries = ['Finland', 'Estonia', 'Sweden', 'Norway']
countries.forEach((country, i) => console.log(i, country.toUpperCase()))

0 "FINLAND"
1 "ESTONIA"
2 "SWEDEN"
3 "NORWAY"

const countries = ['Finland', 'Estonia', 'Sweden', 'Norway']
const newCountries = []
countries.forEach((country) => newCountries.push(country))

console.log(newCountries) // ["Finland", "Estonia", "Sweden", "Norway"]

const numbers = [1, 2, 3, 4, 5]
let sum = 0
numbers.forEach((n) => (sum += n))

console.log(sum) // 15

// syntax in a normal or a function declaration

function callback(item, i) {
  return // code goes here
}

const modifiedArray = array.map(callback)

// or syntax in an arrow function

const callback = (item, i) => {
  return // code goes here
}
const modifiedArray = array.map(callback)

// Using function declaration

const countries = ['Finland', 'Estonia', 'Sweden', 'Norway']

const newCountries = countries.map(function (country) {
  return country.toUpperCase()
})

console.log(newCountries)

// map using an arrow function call back

const countries = ['Finland', 'Estonia', 'Sweden', 'Norway']
const newCountries = countries.map((country) => country.toUpperCase())

console.log(newCountries) // ["FINLAND", "ESTONIA", "SWEDEN", "NORWAY"]

const countries = ['Finland', 'Estonia', 'Sweden', 'Norway']
const countriesLength = countries.map((country) => country.length)

console.log(countriesLength) // [7, 7, 6, 6]

const numbers = [1, 2, 3, 4, 5]
const squares = numbers.map((n) => n ** 2)

console.log(squares) // [1, 4, 9, 16, 25]

// syntax in a normal or a function declaration
function callback(item) {
  return // boolean
}

const filteredArray = array.filter(callback)

// or syntax in an arrow function

const callback = (item) => {
  return // boolean
}
const filteredArray = array.filter(callback)

const countries = ['Finland', 'Estonia', 'Sweden', 'Norway', 'Iceland']
const countriesWithLand = countries.filter((country) =>
  country.includes('land')
)
console.log(countriesWithLand) // ["Finland", "Iceland"]

const countries = ['Finland', 'Estonia', 'Sweden', 'Norway', 'Iceland']
const countriesWithLand = countries.filter(
  (country) => !country.includes('land')
)
console.log(countriesWithLand) // ["Estonia", "Sweden", "Norway"]

const numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
const evens = numbers.filter((n) => n % 2 === 0)
const odds = numbers.filter((n) => n % 2 !== 0)
console.log(evens) // [0, 2, 4, 6, 8, 10]
console.log(odds) // [1, 3, 5, 7, 9]

// syntax in a normal or a function declaration

function callback(acc, cur) {
    return // code goes here
}

const reduced = array.reduce(callback, optionalInitialValue)

// or syntax in an arrow function

const reduced =  callback(acc, cur) => {
    return // code goes here
}
const reduced = array.reduce(callback)

const numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
const sum = numbers.reduce((acc, cur) => acc + cur)
console.log(sum) // 55

const numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
const sum = numbers.reduce((acc, cur) => acc + cur, 5)
console.log(sum) // 60

const strs = ['Hello', 'world', '!']
const helloWorld = strs.reduce((acc, cur) => acc + ' ' + cur)
console.log(helloWorld) // "Hello world !"

const numbers = [1, 2, 3, 4, 5]
const value = numbers.reduce((acc, cur) => acc * cur)
console.log(value) // 120

const numbers = [1, 2, 3, 4, 5]
const value = numbers.reduce((acc, cur) => acc * cur, 10)
console.log(value) // 1200

// syntax in a normal or a function declaration

function callback(item) {
return // code goes here
}

const item = array.find(callback)

// or syntax in an arrow function

const reduced =  callback(item) => {
return // code goes here
}
const item = array.find(callback)

const numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
const firstEvenNum = numbers.find((n) => n % 2 === 0)
const firstOddNum = numbers.find((n) => n % 2 !== 0)
console.log(firstEvenNum) // 0
console.log(firstOddNum) // 1

const countries = ['Finland', 'Estonia', 'Sweden', 'Norway', 'Iceland']
const countryWithWay = countries.find((country) => country.includes('way'))
console.log(countriesWithWay) // Norway

const countries = ['Finland', 'Estonia', 'Sweden', 'Norway', 'Iceland']
const sixCharsCountry = countries.find((country) => country.length === 6)
console.log(sixCharsCountry) // Sweden

const countries = ['Finland', 'Estonia', 'Sweden', 'Norway', 'Iceland']
const index = countries.find((country) => country.includes('o'))
console.log(index // Estonia

// syntax in a normal or a function declaration

function callback(item) {
return // code goes here
}

const index = array.findIndex(callback)

// or syntax in an arrow function

const reduced =  callback(item) => {
return // code goes here
}
const index = array.findIndex(callback)

const numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
const firstEvenIndex = numbers.findIndex((n) => n % 2 === 0)
const firstOddIndex = numbers.findIndex((n) => n % 2 !== 0)
console.log(firstEvenIndex) // 0
console.log(firstOddIndex) // 1

const countries = ['Finland', 'Estonia', 'Sweden', 'Norway', 'Iceland']
const index = countries.findIndex((country) => country.length === 6)
console.log(index //2

const countries = ['Finland', 'Estonia', 'Sweden', 'Norway', 'Iceland']
const index = countries.findIndex((country) => country.includes('o'))
console.log(index // 1

const numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
const someAreEvens = numbers.some((n) => n % 2 === 0)
const someAreOdds = numbers.some((n) => n % 2 !== 0)
console.log(someAreEvens) // true
console.log(someAreOdds) // true

const evens = [0, 2, 4, 6, 8, 10]
const someAreEvens = evens.some((n) => n % 2 === 0)
const someAreOdds = evens.some((n) => n % 2 !== 0)
console.log(someAreEvens) // true
console.log(someAreOdds) // false

const numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
const allAreEvens = numbers.every((n) => n % 2 === 0)
const allAreOdd s= numbers.every((n) => n % 2 !== 0)

console.log(allAreEven) // false
console.log(allAreOdd)  // false

const evens = [0, 2, 4, 6, 8, 10]
const someAreEvens = evens.some((n) => n % 2 === 0)
const someAreOdds = evens.some((n) => n % 2 !== 0)

console.log(someAreEvens) // true
console.log(someAreOdds)  // false

const products = [
  { product: 'banana', price: 3 },
  { product: 'mango', price: 6 },
  { product: 'potato', price: ' ' },
  { product: 'avocado', price: 8 },
  { product: 'coffee', price: 10 },
  { product: 'tea', price: '' },
]

// syntax
class ClassName {
    //  code goes here
}

class Person {
  // code goes here
}

class Person {
  // code goes here
}
const person = new Person()
console.log(person)

Person {}

class Person {
  constructor(firstName, lastName) {
    console.log(this) // Check the output from here
    this.firstName = firstName
    this.lastName = lastName
  }
}

const person = new Person()

console.log(person)

Person {firstName: undefined, lastName}

class Person {
  constructor(firstName, lastName) {
    this.firstName = firstName
    this.lastName = lastName
  }
}

const person1 = new Person('Asabeneh', 'Yetayeh')

console.log(person1)

Person {firstName: "Asabeneh", lastName: "Yetayeh"}

class Person {
  constructor(firstName, lastName) {
    console.log(this) // Check the output from here
    this.firstName = firstName
    this.lastName = lastName
  }
}

const person1 = new Person('Asabeneh', 'Yetayeh')
const person2 = new Person('Lidiya', 'Tekle')
const person3 = new Person('Abraham', 'Yetayeh')

console.log(person1)
console.log(person2)
console.log(person3)

Person {firstName: "Asabeneh", lastName: "Yetayeh"}
Person {firstName: "Lidiya", lastName: "Tekle"}
Person {firstName: "Abraham", lastName: "Yetayeh"}

class Person {
  constructor(firstName, lastName, age, country, city) {
    console.log(this) // Check the output from here
    this.firstName = firstName
    this.lastName = lastName
    this.age = age
    this.country = country
    this.city = city
  }
}

const person1 = new Person('Asabeneh', 'Yetayeh', 250, 'Finland', 'Helsinki')

console.log(person1)

Person {firstName: "Asabeneh", lastName: "Yetayeh", age: 250, country: "Finland", city: "Helsinki"}

class Person {
  constructor(
    firstName = 'Asabeneh',
    lastName = 'Yetayeh',
    age = 250,
    country = 'Finland',
    city = 'Helsinki'
  ) {
    this.firstName = firstName
    this.lastName = lastName
    this.age = age
    this.country = country
    this.city = city
  }
}

const person1 = new Person() // it will take the default values
const person2 = new Person('Lidiya', 'Tekle', 28, 'Finland', 'Espoo')

console.log(person1)
console.log(person2)

Person {firstName: "Asabeneh", lastName: "Yetayeh", age: 250, country: "Finland", city: "Helsinki"}
Person {firstName: "Lidiya", lastName: "Tekle", age: 28, country: "Finland", city: "Espoo"}

class Person {
  constructor(firstName, lastName, age, country, city) {
    this.firstName = firstName
    this.lastName = lastName
    this.age = age
    this.country = country
    this.city = city
  }
  getFullName() {
    const fullName = this.firstName + ' ' + this.lastName
    return fullName
  }
}

const person1 = new Person('Asabeneh', 'Yetayeh', 250, 'Finland', 'Helsinki')
const person2 = new Person('Lidiya', 'Tekle', 28, 'Finland', 'Espoo')

console.log(person1.getFullName())
console.log(person2.getFullName())

Asabeneh Yetayeh
test.js:19 Lidiya Tekle

class Person {
  constructor(firstName, lastName, age, country, city) {
    this.firstName = firstName
    this.lastName = lastName
    this.age = age
    this.country = country
    this.city = city
    this.score = 0
    this.skills = []
  }
  getFullName() {
    const fullName = this.firstName + ' ' + this.lastName
    return fullName
  }
}

const person1 = new Person('Asabeneh', 'Yetayeh', 250, 'Finland', 'Helsinki')
const person2 = new Person('Lidiya', 'Tekle', 28, 'Finland', 'Espoo')

console.log(person1.score)
console.log(person2.score)

console.log(person1.skills)
console.log(person2.skills)

0
0
[]
[]

class Person {
  constructor(firstName, lastName, age, country, city) {
    this.firstName = firstName
    this.lastName = lastName
    this.age = age
    this.country = country
    this.city = city
    this.score = 0
    this.skills = []
  }
  getFullName() {
    const fullName = this.firstName + ' ' + this.lastName
    return fullName
  }
  get getScore() {
    return this.score
  }
  get getSkills() {
    return this.skills
  }
}

const person1 = new Person('Asabeneh', 'Yetayeh', 250, 'Finland', 'Helsinki')
const person2 = new Person('Lidiya', 'Tekle', 28, 'Finland', 'Espoo')

console.log(person1.getScore) // We do not need parenthesis to call a getter method
console.log(person2.getScore)

console.log(person1.getSkills)
console.log(person2.getSkills)

0
0
[]
[]

class Person {
  constructor(firstName, lastName, age, country, city) {
    this.firstName = firstName
    this.lastName = lastName
    this.age = age
    this.country = country
    this.city = city
    this.score = 0
    this.skills = []
  }
  getFullName() {
    const fullName = this.firstName + ' ' + this.lastName
    return fullName
  }
  get getScore() {
    return this.score
  }
  get getSkills() {
    return this.skills
  }
  set setScore(score) {
    this.score += score
  }
  set setSkill(skill) {
    this.skills.push(skill)
  }
}

const person1 = new Person('Asabeneh', 'Yetayeh', 250, 'Finland', 'Helsinki')
const person2 = new Person('Lidiya', 'Tekle', 28, 'Finland', 'Espoo')

person1.setScore = 1
person1.setSkill = 'HTML'
person1.setSkill = 'CSS'
person1.setSkill = 'JavaScript'

person2.setScore = 1
person2.setSkill = 'Planning'
person2.setSkill = 'Managing'
person2.setSkill = 'Organizing'

console.log(person1.score)
console.log(person2.score)

console.log(person1.skills)
console.log(person2.skills)

1
1
["HTML", "CSS", "JavaScript"]
["Planning", "Managing", "Organizing"]