1. Variables and Data Types
JavaScript
Variables and Data Types

2. Holding information

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

4. 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

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

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

7. 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

8. 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

9. VALUES

10. Random Numbers

11. 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!

12. 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!

13. 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.”

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

15. Using JavaScript

16. Class Plan Today: jsfiddle Thursday After break Output
Console.log for helping ourselves
Alerts for “final” results
Thursday
Create “functions” that can be called from the onclick
Output still alerts
After break
Ability to read from forms and write to the page