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CIS101%20Introduction%20to%20Computing

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CIS101 Introduction to Computing Week 12 – PowerPoint PPT presentation

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Title: CIS101%20Introduction%20to%20Computing


1
CIS101 Introduction to Computing
  • Week 12

2
Agenda
  • Your questions
  • Solutions to practice text
  • Final HTML/JavaScript Project
  • Copy and paste assignment
  • JavaScript Loops
  • This week online
  • Next class

3
In class exam
  • Next class meeting
  • Solutions to practice exam posted in Blackboard

4
Final Project
  • Create a Web site using JavaScript/HTML
  • Team project
  • Both members must actively participate in
    presentation (reflected in grade)
  • Topic is up to you, but must be appropriate for
    college assignment
  • See assignments week 12 for details

5
Lesson Topics
  • Introduction to loops
  • The advantages of loops
  • Increment and decrement operators
  • For loop and while loop syntax
  • Controlling loops with conditional expressions

6
Loops
  • A powerful feature computers is the ability to
    repeat steps over and over as many times as
    necessary
  • Programming languages include statements that
    define a section of code that repeats
  • The generic name for a programming statement that
    repeats is a loop
  • The set of statement which is repeatedly executed
    is called the body of the loop

7
Controlling loops
  • Loops repeat code over and over, but eventually
    they do have to stop
  • Common way to control loops is to repeat a
    section of code a certain number of times
  • This requires counting how many times the loop
    has repeated, then stopping when the right number
    has been reached

8
Counting with the increment and decrement
operators
  • JavaScript uses the increment and decrement
    operators for counting
  • Increment means increase (get larger), decrement
    means decrease (get smaller)

9
Increment operator
  • The increment operator adds 1 to the value of
    a variable
  • Example
  • num
  • num both add 1 to value in num
  • Can use before or after the variable

10
Decrement Operator
  • The increment operator -- subtracts 1 from the
    value of a variable
  • Example
  • num--
  • --num both subtract 1 from value in num
  • Can use -- before or after the variable

11
The for Loop
  • The for loop repeats a section of code a specific
    number of times
  • Syntax
  • for (expression1expression2expression3)
  • statements to be repeated go here

12
The for Statement (cont.)
  • The for statement has three parts
  • part 1 Initializes the control variable in
    expression1
  • part 2 Tests expression2. If it is true, the
    body of the loop repeats
  • part 3 Update the value of the control variable
    using expression3
  • Repeats steps 2 and 3,until expression2 becomes
    false

13
The while Loop
  • The while loop is repeats until its condition is
    false
  • Syntax
  • while (condition)
  • Statements to be repeated
  • Where condition is a true or false test

14
The while Loop (cont.)
  • The while loop is implemented using the following
    steps
  • Step 1 The condition is tested to see whether it
    is true or false
  • Step 2 If condition is true, the loop body
    repeats
  • Repeats steps 1 and 2 until condition becomes
    false

15
In the lab
  • You will use loop statements in your code
  • Create a new HTML document using 1st Page 2000
  • Save html file in new folder named Loops on your
    desktop with name lesson0801.htm
  • Copy star.gif from F drive into Loops folder
  • Enter the code on p. 8-10 exactly as you see it
  • Click preview button to test out the code

16
Student Modifications
  • Execute the code on p. 8-10 using different
    values
  • Find and display another image in the loop body
  • Re-write the code using a while loop instead of a
    for loop

17
Shaking the window
  • Code on p. 8-12 uses two loops to shake the
    browser window back and forth
  • One loop inside another is called a nested loop
  • Save your previous work, create a new document
    named lesson0802.htm

18
Shaking the window cont.
  • Copy the code from p. 8-12
  • Save your file, then open it from the browser
  • This will not work in preview mode in 1st Page
    2000

19
Student Modifications (cont.)
  • Modify the code on p. 8-12 as follows
  • Add a second button that calls the function
    shake() with a different value for the parameter
  • Use the onLoad event handler to shake your window
    as soon as it loaded

20
Lesson Summary
  • Loops are sections of code that repeat over and
    over
  • JavaScript statements that repeat include the for
    loop and the while loop
  • The increment operator and the decrement operator
    are used to control loops
  • How to use the onLoad event handler

21
Final Project
  • Use remaining class time to meet with team member
    to plan final project

22
This week online
  • Readings
  • Concepts, chapter 6, Output
  • JavaScript 101 Lesson 08
  • This weeks quiz
  • Concepts, chapter 6, Output

23
Next class meeting
  • In class exam covering Excel, HTML, JavaScript
  • Final presentations during final exam time
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