Variables and Logic

1
Variables and Logic

• Enabling Web Pages to Make Decisions

2
What Is a Variable?

• In computing, a variable is a place in the
  computers RAM that remembers, or stores, the
  value of something changeable.
• It is called a variable because its value is
  subject to change.
• Chapter 10 teaches you how to work with two kinds
  of variables.

3
What Is a String Variable?

• A string is a sequence of one or more
  alphanumeric characters.
• A string variable is a place in computer memory
  that remembers, or stores, the alphanumeric
  characters in a string.

4
What Is a Numeric Variable?

• A numeric variable is a place in computer memory
  that remembers, or stores, a number.
• In a script, the numbers can be integers or
  floating point.
• An integer is a whole number with no decimal
  point.
• A floating point number has a decimal point with
  one or more numbers after the decimal point.

5
Clock Script

• The clock script uses variables to display on
  screen the current date and time.
• One of the best ways to learn about variables is
  to play with them.
• Let us play with the variables in the clock
  script.

6
Chapter 11 Logic

• Chapter 11 teaches you logic by having you
  program a weekly calendar.
• If-Then statements give your scripts the power of
  making decisions.
• Lets play with the calendar script and analyze
  how the If-Then statements work.

7
Functions and Includes

• Chapter 12 teaches you how to create functions
  and includes.
• First you write a countdown function and use it
  to count down to the new year.
• Then you put the countdown function into an
  include file from which you use it to count down
  to your birthday.

8
Javascript Timing

• Chris asked me to talk about how to do timing
  with JavaScript.
• There is a timing function called setTimeout()
  which takes two parameters.
• Lets take a look at how it works in the
  DomEffects example that we will be studying in
  Chapter 15.