Intro to JavaScript
Values, Data Types, Variables
JavaScript: Where did this thing come from?
- 1990s - Netscape, 10 days
- 2000s - The Browser Wars
- 2005 - jQuery
- ~2010 - Front-End Frameworks
- 2012 - Node.js
JavaScript: It's Everywhere
REPL: Read, Evaluate, Print, Loop
Type Code Here
Let's type some things in
> 5
5
> "Hello World"
'Hello World'Type this
Get this
Type this
Get this
What's happening here?
Read
The REPL "Reads" what you typed in
Evaluate
It tries to evaluate it, turning it into a single value
> 5> 5 + 510
What's happening here?
The REPL "Prints" what it Evaluated
Loop
The whole thing starts over
> 5 + 5
10Let's try it
> 5 + 5
> 5 * 6 + 10 * 7
> 44 / 4 * 11
> 55 * 5 * 5 * 5 * 5
> 55 % 10
Type these in
Let's talk about Data Types
Numbers
Strings
Booleans
Null
Undefined
1
5
3.14
5.26
1000000"Hello World"
"Good to meet you"
"These are Strings"
"a"
"123"true
falsenullundefinedLet's talk about Operators
Binary Operators (have two operands)
+ - / * %Takes two numbers, makes another number
+Takes two strings, puts them together
Takes two values, returns a boolean
> < == === != !==| Operator | What it does |
|---|---|
| + | Adds two numbers, concatenates strings |
| - | Subtracts two numbers |
| / | Divides two numbers |
| * | Multiplies two numbers |
| % | Divides two numbers, returns the remainder |
Let's talk about Operators
| Operator | What it does |
|---|---|
| < | Tests to see if one number is less than another |
| > | Tests to see if one number is greater than another |
| == | Tests to see if two values are the same |
| === | Tests to see if two values are the same, and the same type |
| !=, !== | Tests to see if two values are not the same |
| && | Checks to see if two values are both true |
| || | Checks to see if at least one value is true |
Let's talk about Operators
Let's try it!
> true && true
> true && false
> false && true
> true || false
> false || true
> 5 > 10
> 10 < 15
> 5 == 5
> "5" == 5
> "5" === 5
> 5 == "5" && "5" === 5What happened?
Why does true && false give us false?
Why does "5" == 5 give us true? Why does "5" === 5 give us false?
Variables
Think of it like a box with a label
x
var x"var" creates a box, then you give it a label
Variables - The Assignment Operator
x
var x = 55
When we use the assignment operator, we put something in the box
Variables - The Assignment Operator
var x = 5
x = 10We can always reuse the box, but we lose the original value
5
x
10
Variables point to values
var x = 10
var m = 2
var b = 3
var y = m * x + b
var text = "Anyone remember algebra?"| Name | Value |
|---|---|
| x | 10 |
| m | 2 |
| b | 3 |
| y | 23 |
| text | Anyone remember algebra? |
Intro to JavaScript Values, Data Types, Variables
Intro to JavaScript
By LizTheDeveloper
Intro to JavaScript
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