Javascript - Arrays

#100Devs

Leon Noel

Metal Fist terrorists claim responsibility
Broken household name usually said in hostility
Um... what is MF? You silly

Agenda

  • Questions? 

  • Let's Talk -  #100Devs

  • Review - Functions && Loops

  • Learn - Arrays

  • Learn - Array Iteration

  • Learn - Array Methods

  • Homework - Objects

Questions

About last class or life

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Homework: https://forms.gle/PLuuSi7aHeL7wbMQ9

 

Networking

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Coding Challenges

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Programming

A computer will do what you tell it to do.

What is a program?

A program is a set of instructions that you write to tell a computer what to do

What is a programming?

Programming is the task of writing those instructions in a language that the computer can understand.

JAVASCRIPT

Has a specific 'Syntax'

Syntax: "Spelling and grammar" rules of a programming language.

Variables

Declaration: let age

 

Assignment: age = 25

 

Both at the same time:

let age = 25

Conditional Syntax

if(condition is true) {
  //Do this cool stuff
}else if(condition is true){
  //Do this other cool stuff
}else{
  //Default cool stuff
}

🚨 DANGER 🚨

Assignment vs. Comparison

Multiple Conditions

if (name === "Leon" && status === "Ballin"){
 //Wink at camera
}

Multiple Conditions

if (day === "Saturday" || day === "Sunday"){
  //It is the weekend
}

Functions

What are functions?

Functions

  • Functions are simple sets of instructions!

  • Functions are reusable

  • Functions perform one action as a best practice

  • They form the basic "building blocks" of a program

Functions

function name(parameters){
  //body
}

//call
name(arguments)

Functions

function yell(word){
  alert(word)
}


yell("HELLO")

Loops

What are loops?

Loops

  • Repeat an action some number of times!

  • Three main types of loops in Javascript

  • For, while, and do while loops

  • Each type offers a different way to determine the start and end points of a loop

Loops - For

for (let i = 1; i < 5; i++) {
  console.log(i)
}

Loops - While

let count = 0 

while(count < 5){
  console.log(count)
  count++
}

Let's Code

Bring It On - All Or Nothing!

Arrays

What are arrays?

Toasters

Arrays

  • A data structure to store ordered collections!

  • Array elements are numbered starting with zero

  • Arrays have many methods to manage the order of elements

  • Can be created by a constructor or literal notation

Declaring Arrays

let newArr = new Array()

Array Constructor

Declaring Arrays

let newArr = []

Literal Notation

Declaring Arrays

newArr = ['Zebra',true,21]

Arrays are populated with elements

Elements can be of any type

Declaring Arrays

🚨Empty spaces leave an empty element 🚨

Array Indexing

Array Indexing

newArr = ['Zebra',,true,21]

console.log( newArr[0] )  //Zebra
console.log( newArr[1] )  //undefined
console.log( newArr[2] )  //true
console.log( newArr[3] )  //21

Elements can be accessed by their index numbers

Array Indexing

newArr = ['Zebra',,true,21]

newArr[1] = 'Bob'

console.log( newArr )  

// ['Zebra','Bob',true,21]

Elements can be updated by using the index at that position

Array Indexing

let cars = ['Honda', 'Toyota', 'Ford', 'Tesla']
let nums = [1,2,3]
cars = nums
console.log( cars ) //[1,2,3]

You can overwrite whole arrays by assigning an array to a different array

Array Length

console.log( newArr.length ) //4

How do you determine how many elements are in your array?

Let's Code

Array Dat - In It To Win It

Array Iteration

let bestColors = ['green','blue','yellow','black']

for(let i = 0; i < bestColors.length;i++){
  console.log( bestColors[i] )
}

Iterates through an array passing in the value and index of each element 

Array Iteration

let bestColors = ['green','blue','yellow','black']

bestColors.forEach((x,i)=> console.log(x))

Iterates through an array passing in the value and index of each element 

Let's Code

Array Dat - Fight To The Finish

Other Arrays Methods

let bestRappers2020 = ['6ix9ine','Polo G','6ix9ine']

let removed = bestRappers2020.shift()

console.log( bestRappers2020 ) // ['Polo G', '6ix9ine']

Remove item from the beginning of an Array

Other Arrays Methods

let bestRappers2020 = ['Polo G','6ix9ine']

let removedAgain = bestRappers2020.pop()

console.log( bestRappers2020 ) // ['Polo G']

Remove item from the end of an Array

Other Arrays Methods

let bestRappers2020 = ['Polo G']

let removed = bestRappers2020.unshift('Dylan')

console.log( bestRappers2020 ) // ['Dylan','Polo G']

Add item to the beginning of an Array

Other Arrays Methods

let bestRappers2020 = ['Dylan','Polo G']

let removed = bestRappers2020.push('Dylan')

console.log( bestRappers2020 ) // ['Dylan','Polo G','Dylan']

Add item to the end of an Array

Other Arrays Methods

let bestRappers2020 = ['Dylan','Polo G','Dylan']

let bestRappersAllTime = bestRappers2020.map(x => 'Dylan')

bestRappersAllTime.unshift('Dylan')
  
bestRappersAllTime.push('Dylan')

console.log( bestRappersAllTime ) 

// ['Dylan','Dylan','Dylan', 'Dylan', 'Dylan']

Let's Code

Array Dat - Worldwide Cheersmack

Homework

Read: JSWay Arrays
Read: https://javascript.info/array-methods
Read: JSWay Objects
Read: https://eloquentjavascript.net/04_data.html
Do: Minimum of 1 https://codewars.com 8 Kyu Fundamentals Track EVERY DAY - 20 mins then look at solution!
Do: https://javascript30.com Day 04 Array Cardio (super hard, do it on Discord together)