Data Types and Variables

1
Data Types and Variables

• Week 1 - Presentation 2
• Veronica Noone

2
Objectives

• Numerical Data
• Text Data
• Escape Characters
• Boolean Data
• Variables
• Numerical Calculations
• Realistic Example
• Week 01 Lab 02 Pounds to Stone Calculator

3
The What and Why of Data Types

• classification of data that tells the interpreter
  how the programmer intends to use it.
• Kinds of data are important
• 2 2
• Hello World
• JavaScript is Easygoing
• Weakly Typed Language

4
Numerical Data

• Integers (whole numbers)
• 132
• -4
• Floating-point (fractions)
• 1.432
• -54.333
• They do have ranges but are vast

5
Text Data

• String
• hello world
• A
• 123 Any Street
• What if you wanted to work with the phrase
• Todays quote is If at first you don't succeed
  call it version 1.0

6
Escape Characters

• Todays quote is \If at first you don\'t
  succeed call it version 1.0\

7
Boolean Data

• Can only hold one of two variables
• true or false
• Do you want to learn more about JavaScript?
• Yes? Click for the next slide
• No? Leave the room immediately

8
Variables

• A named memory location where we can store data
• Declared with the keyword var
• Names are case sensitive
• No special characters
• No reserved words
• Should MEAN something

var exampleVariable
9
Lets take a Look
ltscript language"javascript" type"text/javascrip
t"gt lt!--// // Declare my first variable var
myFirstVar //assign a value to
myFirstVar myFirstVar "Hello World" //display
myFirstVar in an alert box alert(myFirstVar) //
--gt lt/scriptgt

• Go to the class web page
• Right click on w01p02ex01.html and save the file
  to your desktop

10
Example Questions

• What is the data type of the variable myFirstVar?
• What would happened if we set the variable value
  to something else?
• Lets experiment

11
Experiments

• Can you add a second variable? Give it a try!
• mySecondVar and set its value to 12345
• Now display it
• What if you?
• myFirstVar mySevcondVar
• Display it

12
Numerical Calculations

• Basic Operators
• , -, and /
• Increment and Decrement
• myVar
• myVar myVar 1
• x- -
• x x 1
• Order of precedence applies
• Always use ()

13
Lets take a Look

• Right click on w01p02ex02.html and save the file
  to your desktop
• Fill in the other examples
• Try a increment or decrement
• If this is easy for you PLEASE help you neighbor!

ltscript language"javascript" type"text/javascrip
t"gt lt!--// // example calculations var x var
y var ans //assign values x2 y4 //addition
example ansxy alert(ans) // --gtlt/scriptgt
14
Questions

• What if you added string variables?
• Try it! add 2 more variables called s1 and s2.
• s1 hello
• s2 world
• Add then together and display with an alert.
• What happens? Space issue?

15
Realistic Example
w01p02ex03.html
ltscript language"javascript" type"text/javascrip
t"gt lt!--// var weightInPounds var
weightInKilos //assign values //weightInPounds
150 weightInPounds prompt("Enter your
weight",150) weightInKilos weightInPounds0.453
59 //display myFirstVar in an alert
box document.write("You weigh " weightInKilos
"kg") // --gtlt/scriptgt
16
New statements

• prompt() function
• prompt(text to be displayed,default)
• document.write()
• Document.write(whatever you want)
• Will cover more on this later
• Write is a method of the document object

17
Week 01 Lab 02 Pounds to Stone Calculator

• Code JavaScript that asks the users to enter
  their weight in pounds.
• Convert pounds to stones and display on the page.
  
• Dont know what a stone is? Look it up!
• Lab worth 20 points
• Be sure to comment, use descriptive variable
  names and format the page nicely.
• Email me the link
• this will be the last time we email links - you
  should have your web space set up so I can access
  your past and present labs.
• If that is already the case No email needed