JS Basics

01_types.js

console.log('Hello, world!')


"Hello" // String
'Hello' // String

3 // Number

3.14 // Number

console.log(typeof(3.14))

true // Boolean
false // Boolean

// Base: 0, 1, 2, 3, 4, 5... 10
// 10 - Decimal
let number = Number.parseInt("34", 10)
console.log(typeof(number))

console.log(parseInt("lkhkdhalfklkfjlkj"))
// NaN - Not a Number

null // Representes the absense of a value
undefined // means that a variable or function is not defined


console.log(5 / 4)

01_types.rb

puts "Hello, world!"


"Hello" # String
'Hello' # String

3 # Integer

3.14 # Float

puts 3.14.class

true # TrueClass (Boolean)
false # FalseClass (Boolean)


number = "34".to_i
p number.class


nil # represents the absence of a value
puts "hkahfkhlkaflk".to_i


puts 5 / 4

02_arrays.js

// Array CRUD

// Create
//.                 0        1
const rappers = ['Jay Z', ' Nas']

// Read
console.log(rappers[0])

// Update
rappers.push('Eminem')
console.log(rappers)

rappers[0] = 'Jay Electronica'
console.log(rappers)

// Delete
//        index, no. of el
rappers.splice(-1)
console.log(rappers)

// Splice takes an index an
// an optional number of elements to
// delete
// rappers.splice(0, 2)

const beatles = ['John', 'Paul', 'Ringo', 'George']

// ES6 Syntax
beatles.forEach((beatle) => {
  console.log(beatle.toUpperCase())
})

02_arrays.rb

# Array CRUD

# Create
#.           0       1
rappers = ["Jay Z", "Nas"]

# Read
puts rappers[0]

# Update
# rappers << "Eminem"
rappers.push("Eminem")
p rappers

rappers[0] = "Jay Electronica"
p rappers

# Delete
rappers.delete_at(-1)
p rappers

beatles = ["John", "Paul", "Ringo", "George"]

beatles.each do |beatle|
  puts beatle.upcase
end

03_objects.js

// Objects key => value pairs
// Objects => Hash in Ruby

// Create
const student = {
  firstName: 'John',
  middleName: 'K.',
  lastName: 'Smith'
}
console.log(student)


// Read
console.log(student['firstName'])
// Accepts dot. notation
console.log(student.firstName)

// Update
// student['firstName'] = 'Peter'
student.firstName = 'Peter'
console.log(student.firstName)


// Delete
delete(student.middleName)
console.log(student)


// Iteration
Object.keys(student).forEach((key) => {
  console.log(`The value of ${key} is ${student[key]}.`)
});

03_objects.rb

# Objects key => value pairs
# Hash => Object in JS

# Create
student = {
  first_name: "John",
  middle_name: "K.",
  last_name: "Smith"
}

# Read
puts student[:first_name]

# Update
student[:first_name] = "Peter"
puts student[:first_name]

# Delete

student.delete(:middle_name)
p student

# Iteration
student.each do |key, value|
  puts "The value of #{key} is #{value}."
end

04_variables.js

// Varaibles

// Old JS
var counter = 1
console.log(counter)
counter += 1
// counter = counter + 1
console.log(counter)

// Declare a vsriable without assignment
// var counter
// => undefined

var firstName = "Rui"


// New JS
// const newCounter = 1
// console.log(newCounter)

// newCounter += 1
// TypeError: Assignment to constant variable.
// const variables cannot be reassigned

let newCounter = 1
newCounter += 1
console.log(newCounter)

04_variables.rb

# Variables

# Ruby you declare and assign
counter = 1
puts counter
counter += 1
# counter = counter + 1
puts counter


first_name = "Rui"

05_interpolation.js

firstName = "Rui"
lastName = "Freitas"


// Old JS (concatenation)
// var sentence = firstName + ' ' + lastName
// console.log(sentence)

// ES6 Js - Template literals
const sentence = `${firstName} ${lastName}`
console.log(sentence)

05_interpolation.rb

first_name = "Rui"
last_name = "Freitas"

puts "Hello, #{first_name} #{last_name}"

06_control_flow.js

const age = 17

if (age >= 18) {
  console.log('You can vote!')
}
else {
  console.log("You're too young! Go home")
}


// Ternary operator
const raining = false
const accessory = raining ? 'umbrella' : 'sunglasses'
console.log(accessory)

// JS does type coersion
// careful with == comparisons
const digit = '0'
if (digit === 0) {
  console.log('Zero')
} else if (digit === 1) {
  console.log('One')
} else {
  console.log('Sorry, I dont know that number')
}

06_control_flow.rb

age = 18

if age >= 18
  puts "You can vote!"
else
  puts "You're too young! Go home!"
end

# Ternary operator
raining = false
accessory = raining ? "umbrella" : "sunglasses"
puts accessory


digit = "0"
if digit == 0
  puts "Zero"
elsif digit == 1
  puts "One"
else
  puts "Sorry, I don't know that number!"
end

07_capitalize.js

// Methods are called functions


// Old JS
function greeting(name = 'Stranger') {
  return 'Hello, ' + name + '!'
}

// In JS parenthesis are not optional
console.log(greeting())
console.log(greeting('John'))

// ES6 syntax
// Arrow functions: () => {}
const newGreeting = (name = 'Stranger') => {
  return `Hello, ${name}!`
}
console.log(newGreeting());
console.log(newGreeting('Mike'))

const capitalize = (string) => {
  return string[0].toUpperCase() + string.slice(1, string.length).toLowerCase()
}

console.log(capitalize('sUSAn'))

07_capitalize.rb

# Method declaration
def greeting(name = "Stranger")
  # return "Hello, #{name}!"
  # Ruby has implicit returns
   "Hello, #{name}!"
end

puts greeting # greeting() optional
puts greeting("John")


def myCapitalize(string)
  # Grab the first letter
  # upcase thr first letter
  # Grab the rest
  # Downcase the rest
  # join them together
  string[0].upcase + string[1..-1].downcase
end

puts myCapitalize("sUsAN")