Javascript - OOP

Leon Noel

#100Devs

And I was thinking 'bout starting up my own school
A Montessori
And the hallway looking like a monastery, oh yes
I'm way up, I feel blessed

Agenda

• Questions? 
• Let's Talk -  #100Devs
• Learn - Objects
• Learn - Basic OOP Principles
• Do - Work In Teams: Tic-tac-toe
• Homework - Object City Yall

Questions

About last class or life

Checking In

Trough Of Sorrow

No Networking Until May

Client Deadline: March 5th

Client Alternatives

Grassroots Volunteer*

Free Software / Open Source

https://www.firsttimersonly.com/

Live Crafting Your Story

FRIDAY
6:30pm EST

OFFICE HOURS

SUNDAY
1:00pm EST

Objects

What are objects?

USE
UNDERSTAND
BUILD

Finna Make Sum Nerds Angry

Objects

• Objects are a collection of variables and functions!
• Objects represent the attributes and behavior of something used in a program
• Object variables are called properties and object functions are called methods
• Objects store "keyed" collections

Think of a physical object

What are it's attributes and behaviors? 

How about a stopwatch

What are its attributes and behaviors? 

Stopwatch Object

• Properties (attributes):
  Might contain a variable to represent hours, another to represent minutes, and another to represent seconds. 

 

 

• Methods (behaviors):
  Might also contain functions that manipulate those values, such as "start ()" and "stop ()".

Stopwatch Object

let stopwatch = {}

stopwatch.currentTime = 12

stopwatch.tellTime = function(time){
  console.log(`The current time is ${time}.`)
}

stopwatch.tellTime(stopwatch.currentTime)

Notation?

Objects

What if we want to make

a lot of objects?

How much money you got? How many problems you got? How many people done doubted you? Left you out to rot?

Car Factory?

Constructors then Classes

Car Factory

Constructor

function MakeCar(carMake,carModel,carColor,numOfDoors){
  this.make = carMake
  this.model = carModel
  this.color = carColor
  this.doors = numOfDoors
  this.honk = function(){
    alert('BEEP BEEP FUCKER')
  }
  this.lock = function(){
    alert(`Locked ${this.doors} doors!`)
  }
}

let hondaCivic = new MakeCar('Honda','Civic','Silver', 4)

let teslaRoadster = new MakeCar('Tesla','Roadster', 'Red', 2)

Car Factory

We forgot enable bluetooth! 

let teslaRoadster = new MakeCar('Tesla','Roadster', 'Red', 2)

console.log( teslaRoadster.bluetooth )  //undefined

MakeCar.prototype.bluetooth = true

console.log( teslaRoadster.bluetooth ) //true 

A prototype is another object that is used as a fallback source of properties

Car Factory

Why does .toString() work?!?

let teslaRoadster = new MakeCar('Tesla','Roadster', 'Red', 2)

console.log( teslaRoadster.doors.toString() )  // "2" not 2

A prototype is another object that is used as a fallback source of properties

Car Factory

Look Ma! New syntax!

class MakeCar{
  constructor(carMake,carModel,carColor,numOfDoors){
    this.make = carMake
    this.model = carModel
    this.color = carColor
    this.doors = numOfDoors
  }
  honk(){
    alert('BEEP BEEP FUCKER')
  }
  lock(){
    alert(`Locked ${this.doors} doors!`)
  }
}

let hondaCivic = new MakeCar('Honda','Civic','Silver', 4)

let teslaRoadster = new MakeCar('Tesla','Roadster', 'Red', 2)

Classes are like templates for objects!

Let's Code

Objects - Espresso Machine

BUT WHY?

Why Use Objects?
Why Would We Need A Factory?

As our codebase gets larger and more folx join the team, can we keep our code organized?

Is it easy to add new features and functionality?

Can another developer look at my code and understand what is happening?

Can I make changes without losing sleep at night? 

What if there was a system, a paradigm, a set of rules, an agreed upon way to structure our code that:

Made it easier to add new stuff

Made it easier to read through what was already coded

And made it so you were not afraid to make changes

Music & Light Warning - Next Slide

OOP BABY

OBJECT ORIENTED PROGRAMING 

Let's See Some Code

let hourlyRate = 250
let hours = 160
let taxRate = .35

function calculateProfit(rate, numOfHours, taxes){
  return rate * numOfHours * (1 - taxes)
}

let profit = calculateProfit(hourlyRate, hours, taxRate)

console.log(profit)

Is it easy to add new features and functionality?

let hourlyRate = 250
let hours = 160
let taxRate = .35

function calculateProfit(rate, numOfHours, taxes){
  return rate * numOfHours * (1 - taxes)
}

function holdForTaxes(profitMade){
  return hourlyRate * hours - profitMade
}

let profit = calculateProfit(hourlyRate, hours, taxRate)

let taxesHeld = holdForTaxes(profit)

console.log(profit)

console.log(taxesHeld)

Can another developer look at my code and understand what is happening?

let hourlyRate = 250
let hours = 160
let taxRate = .35

function calculateProfit(rate, numOfHours, taxes){
  return rate * numOfHours * (1 - taxes)
}

function holdForTaxes(profitMade){
  return hourlyRate * hours - profitMade
}

let profit = calculateProfit(hourlyRate, hours, taxRate)

let taxesHeld = holdForTaxes(profit)

console.log(profit)

console.log(taxesHeld)

let hourlyRate = 250
let hours = 160
let taxRate = .35

function calculateProfit(rate, numOfHours, taxes){
  return rate * numOfHours * (1 - taxes)
}

let profit = calculateProfit(hourlyRate, hours, taxRate)

console.log(profit)

Can I make changes without losing sleep at night? 

let hourlyRate = 250
let hours = 160
let taxRate = .35

function calculateProfit(rate, numOfHours, taxes){
  return rate * numOfHours * (1 - taxes)
}

function holdForTaxes(profitMade){
  return hourlyRate * hours - profitMade
}

let profit = calculateProfit(hourlyRate, hours, taxRate)

let taxesHeld = holdForTaxes(profit)

console.log(profit)

console.log(taxesHeld)

DATA & FUNCTIONALITY

let hourlyRate = 250
let hours = 160
let taxRate = .35

DATA

Functionality

function calculateProfit(rate, numOfHours, taxes){
  return rate * numOfHours * (1 - taxes)
}

let seriousBusinessPerson = {
  hourlyRate: 250,
  hours: 160,
  taxRate: .35,
  calculateProfit: function() {
    return this.hourlyRate * this.hours * (1 - this.taxRate)
  }
}

Is it easy to add new features and functionality?

let seriousBusinessPerson = {
  hourlyRate: 250,
  hours: 160,
  taxRate: .35,
  calculateProfit: function() {
    return this.hourlyRate * this.hours * (1 - this.taxRate)
  }
}

let seriousBusinessPerson = {
  hourlyRate: 250,
  hours: 160,
  taxRate: .35,
  calculateProfit: function() {
    return this.hourlyRate * this.hours * (1 - this.taxRate)
  }
  calculateTaxesHeld: function(){
    return this.hourlyRate * this.hours - this.calculateProfit()
  }
}

Can another developer look at my code and understand what is happening?

let seriousBusinessPerson = {
  hourlyRate: 250,
  hours: 160,
  taxRate: .35,
  calculateProfit: function() {
    return this.hourlyRate * this.hours * (1 - this.taxRate)
  }
}

Can I make changes without losing sleep at night? 

let seriousBusinessPerson = {
  hourlyRate: 250,
  hours: 160,
  taxRate: .40, //changed
  calculateProfit: function() {
    return this.hourlyRate * this.hours * (1 - this.taxRate)
  }
}

This fusion of data and functionality into one object

Music & Light Warning - Next Slide

Encapsulation Baby

Encapsulation

The process of storing functions (methods) with their associated data (properties) - in one thing (object)*

*Nerds shaking violently

Is it easy to add new features and functionality?

Heats water for espresso and steam for your milk

Steam wand sucks...

What should the engineers do?

Do they get rid of the water boiler?

probably not...

At first, do they even need to think about the water boiler?

So the water boiling is abstracted?

Let's look at some code

function AgencyContractor(hourlyRate, hours, taxRate){
  this.hourlyRate = hourlyRate
  this.hours = hours
  this.taxRate = taxRate
  this.calculateProfit = function() {
    return this.hourlyRate * this.hours * (1 - this.taxRate)
  }
  this.invoiceClient = function(){
    return `Your invoice total is ${this.hourlyRate * this.hours}`
  }
}

let leon = new AgencyContractor(250,160,.35)
console.log( leon.invoiceClient() ) //40000
console.log( leon.hourlyRate ) //250
console.log( leon.calculateProfit() ) //26000

Ut Oh...

I PUT THIS CALCULATOR ON OUR AGENCY WEBSITE...

function AgencyContractor(hourlyRate, hours, taxRate){
  this.hours = hours
  this.taxRate = taxRate
  let rate = hourlyRate
  let calculateProfit = function() {
    return rate * this.hours * (1 - this.taxRate)
  }
  this.invoiceClient = function(){
    return `Your invoice total is ${rate * this.hours}`
  }
}

let leon = new AgencyContractor(250,160,.35)
console.log( leon.invoiceClient() ) //40000
console.log( leon.hourlyRate ) //undefined
console.log( leon.calculateProfit() ) 
//Uncaught TypeError: leon.calculateProfit is not a function

Better...

*Nerds shaking violently

So now my client can still get their invoice, but not see my hourly rate

Water boiling was hidden from the steam wand

Hourly rate was hidden from the client

Complex or unnecessary details are hidden

This enables you to implement things without understanding or even thinking about all the hidden complexity

Smaller more manageable pieces of code

Do stuff once

Music & Light Warning - Next Slide

Abstraction Baby

Abstraction

Hide details

and show essentials

SIMPLE, PREDICTABLE, MANAGEABLE

The Four Pillars

What if they actually made any sense...

Encapsulation

The process of storing functions (methods) with their associated data (properties) in one thing (object)

BUT WHY?

Abstraction

Hide details

and show essentials

BUT WHY?

Inheritance

Polymophism

Next Class

Group Work

https://live.remo.co/e/100devs-objects-project

Right Of Passage

Get It To Work 

Then:
 

Make it easier to add new stuff

Make it easier to read through what was already coded

And make it so you are not afraid to make changes

Homework