Data Types

Welcome to Class
Go over the Learning Objectives
draw Git chart on board for review

Review: Git & Terminal

What is Git?
How does Git work?
Why do we use Git?
Fill in the chart:
- making changes
- staging
- committing
- pushing
  - fetch
  - merge
- pulling
- remote vs local

Where are we?

spent the last two classes downloading and learning a set of tools:
- Git
- Terminal
- Node & NPM
Next 4 classes are when we're going to learn how to write programs
Start at the beginning/most atomic unit of any program, which is the data passing through that program
every class is going to build of the ones before it and by the end we'll know just about everything about the language we need in order to write and build programs
to draw an analogy, in your Language Arts or English classes in High School and maybe College, you learned about subjects, verbs, punctuation, sentence structure, paragraph structure, etc - since JavaScript is a language it's helpful to think about what we're learning over the next few weeks as synonymous in a lot of ways
- instead of sentences and paragraphs, we have expressions and statements
- instead of subjects and verbs, we have values and operators

Introduction to Data Types

At the most generalized level of discussing programming, all we're doing is moving and manipulating data.

What is a "Data Type"

Data types are simply the kinds of data that we can work with within our program
more nuanced than saying we can use numbers, strings, booleans, etc
data types determine what the possible values can be in any given part of our program
data types also determine what actions we can perform on our data --> Values and Operators

Two ways of classifying data types: Simple or Basic Data Types and Complex Data Types

Today, we're talking about Simple Data Types:

Numbers
Strings
Booleans

We'll get in to our first Complex data type: Arrays
For each data type we cover, we'll answer these two questions:
- What values constitute this data type?
- What operations can I perform on this data type?

Numbers

What values constitute Numbers?
What operations can we perform on Numbers?

Numeric Values

Numbers are numeric values stored in computer memory
It's important to note that there is a limit to the size of numbers you can work with - but you wont need to worry about it, because it's really big
JavaScript Numbers can be integers or floats integers: whole numbers like 1, 10 or -100 floats: fractional numbers like 1.2, 3.14, 0.25
That's kind of it as far as what we need to worry about when it comes to numeric data
There are a lot of use cases for numeric data in JavaScript
- numeric data: number of people on the bus
- numbers as information: the score in a game we're building
- numbers as attributes: the x and y coordinates of an element on the screen that we want to animate

Operators

Arithmetic Operators
Number Operators (Math object)

Arithmatic operators

Addition:

console.log( 'Addition:' )
console.log( 1 + 1 ) // => 2

Subtraction:

console.log( 'Subtraction:' )
console.log( 2 - 5 ) // => -3

Division:

console.log( 'Division:' )
console.log( 5 / 1 ) // => 2.5

Multiplication:

console.log( 'Multiplication:' )
console.log( 6 * 2 ) // => 12

Modulo/Remainder:

console.log( 'Modulo:' )
console.log( 10 % 2 ) // => 0
console.log( 5 % 2 ) // => 1

Special Number Operators

Math object

Absolute value

console.log( 'Absolute value:' )
console.log( Math.abs( 12.234 ) )
console.log( Math.abs( 0.1 + 0.2 ) )

Power

console.log( 'Power:' )
console.log( Math.pow( 3, 2 ) ) // => 9

Square root

console.log( 'Square root:' )
console.log( Math.sqrt( 4 ) ) // => 2

Random Number

console.log( 'Random Number:' )
console.log( Math.random() ) // => 0.229375290430

How might I get a random number between 0 and 10

Math.floor( Math.random() * ( max - min + 1 ) + min );

Strings

What values constitute Strings?
What operations can we perform on Strings?

String Values

strings are made up of characters and stored within single or double quotes
- can be either single or double quotes - important that the outermost quotes are the same and any inner quotes are the opposite
We use string values a lot to represent text data - names, addresses, anything!

'hello world'
"hello world"
"hello 'world', hello"

String Operations

Concatenation - adding two strings together
String methods

Concatenation

'hello ' + 'world'
'I have ' + 20 + ' dogs!'

String Methods

'hello'.toUpperCase()
'HeLLo'.toLowerCase()

Exercise

console.log( 'zachary ' + 'fleischmann' )
console.log( 'zachary'.charAt(2) + 'zacary'.charAt(4) + 'zachary'.charAt(0) )

Booleans

What values constitute Booleans?
- something is either true or false
- Sort of it
- where this gets interesting is in what we use Booleans for - which is a lot
What operations can we perform on Booleans?
- Logical Operators - set of operators based on whether something is true or false
- and, or and not
- we care about what this evaluates to
- evaluated values - any expression can evaluate to true or false

Value

only true and false

Operations

Logical operators
Evaluated expressions

Logical Operators

Logical And ( && )

console.log( true && true ) // => true
console.log( true && false ) // => false
console.log( false && false ) // => false

Logical Or ( || )

console.log( true || true ) // => true
console.log( true || false ) // => true
console.log( false || false ) // => false

Logical Not ( ! )

console.log( !true ) // => false
console.log( !false ) // => true

Evaluated Expressions

Comparison operators ==, ===, >, <, >=, <= True

console.log ( 1 == 1 ) // => true

False

console.log( 4 < 2 ) // => false

Combining them

console.log( !( 4 < 2) ) // => true

Variables

stepping away from data types into using our data
want to store our data somewhere where we can reuse it and perform calculations and other operations on it

Gives meaning to our data:

a 4 is no longer just a 4 but the number of people sitting in the front row
a string is no longer just a string but someone's name
Two parts to creating a variable
- declaring it and
- assigning it a value

var myFirstVariable
myFirstVariable = 'Hello World'

If we just declare a variable, it's value is undefined

var myFirstVariable = 'Hello World'

call a variable to get it's value, which we do by referencing it's name

Type Checking

We can check the type of a variable by using typeof(), which returns a string for the variable's type (i.e. 'number', 'string')

var a = 1
console.log( typeof( a ) ) // => 'number'

var b = 'hey'
console.log( typeof( b ) ) // => 'string'

var c = true
console.log( typeof( c ) ) // => 'boolean'

var d
console.log( typeof( d ) ) // => 'undefined'

Type Conversion

we can convert a variable from one type to another
we can convert a variables type by using conversion methods like toString()

var e = 5
console.log( typeof( e ) ) // => 'number'
e = e.toString()
console.log( typeof( e ) ) // => 'string'
e = parseInt(e)
console.log( typeof( e ) ) // => 'number'
e = e + '0'
console.log( typeof( e ), e ) // => 'string' 50
e = undefined
console.log( typeof( e ) ) // => 'undefined'

Arrays

Quick review - we now know numbers, strings, booleans - all of the basic data types
we also know how to save data of these basic data types into variables so that we can reuse it elsewhere and actually work with that data
what we will quickly find is that we need an efficient way of organizing our data into more than just individual variables and one way to do that is with arrays!
in some other programming languages, arrays are called lists and I think that's a better way to describe what arrays are and what they do - it's a list of data

[1, 2, 3, 4, 5]

Array Indexes

once we've got our data into a list, we want to work with it
How do I get the first value of an array?
Indexes are 0 based - meaning the first item is 0

var myOnlyFriends = ['Moe', 'Larry', 'Curly']

console.log( myOnlyFriends[0] ) // => 'Moe'
console.log( myOnlyFriends[1] ) // => 'Lary'
console.log( myOnlyFriends[2] ) // => 'Curly'

Array Length

the length of array is equal to the number of elements in the array
always one larger than the index for the last element within the array

console.log( myOnlyFriends.length ) // => 3
console.log( myOnlyFriends[ myOnlyFriends.length ] ) // undefined
console.log( myOnlyFriends[ myOnlyFriends.length - 1 ] ) // 'Curly'

Array Methods

There are a ton of methods we can perform on arrays natively
these let us efficiently perform some basic operations on arrays, like adding and removing elements from the beginning and end of arrays

remove and return the last element from an array console.log( myOnlyFriends.pop() ) // => 'Curly'

Add an item to the end of an array console.log( myOnlyFriends.push( 'Christine' ) ) // => [ 'Christine', 'Moe', 'Larry', 'Curly' ]

Reverse the order of items within an array console.log( myOnlyFriends.reverse() ) // => [ 'Curly', 'Larry', 'Moe' ]

Concatenate elements of an array together into a string console.log( myOnlyFriends.join() ) // => 'Moe,Larry,Curly'

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lesson_plan.md

lesson_plan.md

Data Types

Review: Git & Terminal

Where are we?

Introduction to Data Types

What is a "Data Type"

Numbers

Numeric Values

Operators

Arithmatic operators

Special Number Operators

Strings

String Values

String Operations

Concatenation

String Methods

Exercise

Booleans

Value

Operations

Logical Operators

Evaluated Expressions

Variables

Type Checking

Type Conversion

Arrays

Array Indexes

Array Length

Array Methods

Files

lesson_plan.md

Latest commit

History

lesson_plan.md

File metadata and controls

Data Types

Review: Git & Terminal

Where are we?

Introduction to Data Types

What is a "Data Type"

Numbers

Numeric Values

Operators

Arithmatic operators

Special Number Operators

Strings

String Values

String Operations

Concatenation

String Methods

Exercise

Booleans

Value

Operations

Logical Operators

Evaluated Expressions

Variables

Type Checking

Type Conversion

Arrays

Array Indexes

Array Length

Array Methods