1. Reviewing key concepts
JavaScript
Reviewing key concepts

2. 3 BIG IDEAS
Assignment Statements
Functions
Forms

3. Idea 1: assignment statements

4. Holding information A computer doesn’t understand values
It takes locations and does what you tell it
It knows about “cubby holes”
A JavaScript Statement
Takes information from a cubby hole
Does what you say
And then puts it where you say
Holding information

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

6. CUBBY HOLES 3 types of cubby holes Differences Fields in a form
Function input and output
Specially defined ones
Differences
Some you can only read
Some you can only write
Some you can do both
CUBBY HOLES

7. using Functions

8. Output
Black Box
Inputs

9. Return Parameters Function Cubby hole I can just write
Cubby holes I can just read

10. Isolation A function can be called from ANYWHERE
It knows nothing about the outside world
You need to tell it EVERYTHING it needs
Isolation

11. The rules The order of the parameters matter Only a single output
5 - 3 different than 3 -5
Any number of parameters can be defined
Fixed for any specific function
Only a single output
Optional in general
Same for any specific function
The rules

12. Returning a value Use the function as a value Contrast with
form.field.value = function(parm1, parm2);
difference = subtract(minuhend,subtrahend);
Contrast with
alert(string);
append(form.field.value,’end’);
Returning a value

13. creating Functions

14. Writing: alert, log
Conversions: strings and numbers
Many more: google them
Existing functions

15. Need to define
Inputs
Outputs
What to do
Building our own

16. Inputs: read only These are the parameters
Order matters
Need a way to reference them
Position 1, position 2, …
Cubby holes
Better to use meaningful names
Each name is just a pointer to the cubby hole
Inputs: read only

17. output: write once Use a RETURN statement
A write-once cubby hole
Only way to access is the RETURN statement
Once you set it, the function is ended
Can have a simple value or more (e.g., concatenating strings)
output: write once

18. WHAT TO DO Series of statements: the recipe Can use
Assignment statements
Function calls
Can use
Literals (5, “ “)
parameters
Specially defined locations (variables)
WHAT TO DO

19. Idea 3: Forms

20. Form fields are cubby holes
Two cubby holes that we have learned about:
value: something that can be changed
src: the picture file
Form fields are cubby holes