Increment/Decrement Operators ++ increases value by one x++ x =
x + 1 -- decreases value by one x-- x = x 1 Pre/post version ++x
vs. x++ --x vs. x--
Slide 5
Assignment Operators += -= *= %=
Slide 6
Designing Using Pseudocode So far we have focus on the syntax
and semantics As the complexity of problems increases you need a
design strategy (algorithm) to solve such problems Several
alternatives exist to come up with a solution to a problem. A
popular one is Pseudocode Pseudocode: English-like description of
the set of steps required to solve a problem When you write
pseudocode you focus on determining the steps necessary to solve a
problem without worrying about programming language syntax
issues
Slide 7
Pseudocode Example Pseudocode for finding the minimum value 1.
Read number of values to process (call this value n) 2. Repeat the
following steps until the n input values have been processed a.
Read next value into x b. If (x is the first value read) {
currentMinimum = x } else { if (x < currentMinimum) {
currentMinimum = x } } 3. Print currentMinimum value
Slide 8
Suggestions for Solving Problems Using a Programming Language
Pseudocode Make sure you have written pseudocode. Try to verify
(e.g., trace tables) that your pseudocode is correct Do not wait
until the last minute Code implementation could be unpredictable
Incremental code development Fundamental principle in computer
programming. Write a little bit of code, and make sure it works
before you move forward Dont make assumptions If you are not clear
about a language construct, write a little program to familiarize
yourself with the construct Good Indentation From the get-go use
good indentation as it will allow you to understand your code
better
Slide 9
Suggestions for Solving Problems Using a Programming Language
Good variable names Use good variable names from the get-go Testing
Test your code with simple cases first Keep backups As you make
significant progress in your development, make the appropriate
backups Trace your code Use a debugger Take breaks If you cannot
find a bug take a break and come back later
Slide 10
do while Statement do while statement Allows repetition of a
set of statements Basic Form do { statement (s)// executed as long
as expression is true } while (expression); Notice the semicolon
after the expression parenthesis Executes the statement at least
once Example: DoWhileNumbers.html, DoWhile.html Any type of
statements (including do whiles) in a do while When to use a do
while? When to use a while?
Slide 11
Introduction to Functions Function An entity that completes a
particular task for us It can take values necessary to complete a
particular task It can return values After completing a task it
returns to the point after the call Examples of JavaScript
functions document.writeln alert() You can define your own
functions
Slide 12
Introduction to Functions General form of a function is:
function name ( ) { statements } Functions are invoked by using the
() operator A function can receive values via parameters Some
functions may not return a value Some functions may not take any
parameters There are other approaches to define functions Example:
Restaurant.html
Slide 13
Functions Returning Values A function can return a value via
the return statement return expression; A call to a function that
returns a value can be used as an expression The function execution
terminates when a return statement is executed A return statement
with no return value terminates the function execution The return
can occur in a repetition statement Can we return more than one
value? Example: FunctionReturn.html
Slide 14
Conventions to Use From Now on Variable/Function names We will
use lowercase If multiple words are associated with a variable name
then capitalize the first letter of second word on waterTemperature
globalWarmingIndex Curly Brackets Use a particular style
Comparisons Use === rather than == No global variables! Good
indentation
Slide 15
Global/Local Variables Global Variables variables defined
outside of any function Lets see an example We want to avoid using
global variables. Why? Variables declared in a function are called
local variables. They are created on entry to the function and
destroy on exit You can use the same name in different functions as
they are different variables
Slide 16
For Loop Iteration statement General form for (initialize;
test; expression) statement basically equivalent to Initialize
while (test) { statement expression } If more than one statement
use { } Example: ForLoop.html
Slide 17
One-Dimensional Arrays Problem: You need to keep track of the
scores of students in a class Declaring and handling 50 variables
is not an easy task Arrays come to the rescue Array Collection of
values that can be treated as a unit or individually var a = new
Array(4) You can visualize an array as a set of variables one after
another Indexing We access an element using [ ] First element
associated with index 0 (e.g., a[0]) An element of an array can be
of any type and an array can hold different types of elements The
length property represents the length of the array (e.g., a.length)
We can print the contents of an array by using alert For loops are
often used with arrays Example: ArrayEx.html What happens when we
assigned one array variable to another? How do we make a copy of an
array? How do we check whether two arrays are the same?
Slide 18
Passing Values to Function Mechanism used to pass values to
function is called pass- by-value Parameters Variables that receive
data There are normal variables Arguments Values you pass to a
function Example: PassByValue.html Does it matter how we name the
parameters?
Slide 19
Passing Values to Function How are arrays passed to functions?
Example: PassReturnArrays.html Memory Diagram Tool we will use to
illustrate the associations between variables and entities (e.g.,
objects, arrays, etc.)
Slide 20
What is null? What does it represents? When can use null?
null
Slide 21
Functions as Data In JavaScript functions are considered data
That means they can be assigned to variables, stored as properties
of objects or elements of arrays, passed as arguments to functions,
etc. Lets write a function that displays hello and then create an
alias to this function Example: FunctionsAsData.html