1. Variables and Data Types
JavaScript
Variables and Data Types

2. WiLL CONNECT BACK TO HTML NEXT WEEK
OUTPUT WITHOUT ALERT
Console.log();
WiLL CONNECT BACK TO HTML NEXT WEEK

3. Holding information

4. Holding information Computer doesn’t understand values
It knows about locations: “cubby holes”
Takes locations and does what you tell it: read, write, add

5. A = B + C; example Cubby Hole 2: add this value
Cubby Hole 3: place it here
A = B + C;
Cubby Hole 1: take this value

6. Defining CUBBY HOLES They are called variables Define them
Give them values
Take values from them

7. = means “takes the value of” A = B + C; A takes the value of B+C

8. Changing Information A = A + C; Cubby Hole 2: add this value
Cubby Hole 1: replace the old value
A = A + C;
Cubby Hole 1: take this value

9. To DEFINE
var anyName; Defines a variable called anyName Case-sensitive Can be any type of value var aNumber = 1; aNumber is a number Starts with a value of 1

10. VALUES

11. What values can it take? Any “expression” What is an expression?
Variables
Constants
Operators
functions
Different for numbers and strings

12. Numbers
Regular math operators
Variables
Constants
Functions

13. Random Numbers

14. Why random numbers? Variability Different results Examples
Display one of ten pictures
Display one of five quotations
Play a game of chance
All built on a random number!

15. Can computers really create random numbers?
Computers do as they are told
So how can they do something random?
They can’t!
But we can tell them to find a number that changes often!
Needs to not have an easily recognized pattern
Pseudo-random Number Generator
Options?
Time!

16. Getting a random number
Math.random()
Returns a value between 0 and 1
One of a series of mathematical functions
members of a collection called Math
each are prefixed by “Math.”

17. What if you don’t want 0-1? Change range? Multiply Not start at 0? Add
Integers only?
Round
Floor
Ceiling

18. Strings Think of Scrabble tiles Each tile is a Letter Number
Punctuation mark
Space (blank)

19. What is a String?
A literal string must be inside double quotes or single quotes
“this is a string” and this is not a string.
Remember to beware cut and paste

20. Concatenating (formally)
It means combining two or more things into one thing
+ Anything can be concatenated
“awe” & “some” = “awesome”
Whitespace only matters inside quotes
“a”+“b” same as “a” + “b”
“a ” + “b” NOT the same as “a” + “b”

21. Substring A substring is also a String
A substring is a part of another string
“cake” is a substring of “birthday cake”
so are “day”, “thd”, and “y cake”
“they” is not, neither is “hello” or “dude”
Will come back to how to extract substrings

22. Referencing characters
Each character has a position
Note that it starts at 0, not 1 H I M O 1 2 3 4 5