Sams Teach Yourself JavaScript in 24 Hours

By Michael Moncur

• Table of Contents
  • Copyright
  • About the Author
  • Acknowledgments
  • We Want to Hear from You!
  • Reader Services
  • Introduction
  • Part I: Getting Started
  • Hour 1. Understanding JavaScript
  • Hour 2. Creating a Simple Script
  • Hour 3. How JavaScript Programs Work
  • Part II: Learning JavaScript Basics
  • Hour 4. Using Functions and Variables
  • Hour 5. Using Strings and Arrays
  • Hour 6. Testing and Comparing Values
    • The if Statement
    • Using Shorthand Conditional Expressions
    • Using Multiple Conditions with switch
    • Workshop: Evaluating a User Response
    • Summary
    • Q&A
    • Quiz
    • Exercises
  • Hour 7. Repeating Yourself: Using Loops
  • Hour 8. Using Math and Date Functions
  • Part III: The Document Object Model (DOM)
  • Hour 9. Working with the Document Object Model
  • Hour 10. Responding to Events
  • Hour 11. Using Windows and Frames
  • Hour 12. Getting Data with Forms
  • Hour 13. Using Graphics and Animation
  • Part IV: Moving on to Advanced JavaScript Features
  • Hour 14. Creating Cross-Browser Scripts
  • Hour 15. Creating Custom Objects
  • Hour 16. Working with Sounds and Plug-Ins
  • Hour 17. Debugging JavaScript Applications
  • Part V: Working with Dynamic HTML (DHTML)
  • Hour 18. Working with Style Sheets
  • Hour 19. Using Dynamic HTML (DHTML)
  • Hour 20. Using Advanced DOM Features
  • Part VI: Putting It All Together
  • Hour 21. Improving a Web Page with JavaScript
  • Hour 22. Creating a JavaScript Game
  • Hour 23. Creating DHTML Applications
  • Hour 24. JavaScript Tips and Tricks
  • Part VII: Appendices
  • Appendix A. Other JavaScript Resources
  • Appendix B. Tools for JavaScript Developers
  • Appendix C. Glossary
  • Appendix D. JavaScript Quick Reference
  • Appendix E. DOM Quick Reference

Using Multiple Conditions with switch

Often, you'll use several if statements in a row to test for different conditions. Here is one example of this technique:

if (button=="next") window.location="next.html";
if (button=="previous") window.location="prev.html";
if (button=="home") window.location="home.html";
if (button=="back") window.location="menu.html";

Although this is a compact way of doing things, this method can get messy if each if statement has its own block of code with several statements. As an alternative, JavaScript includes the switch statement, which allows you to combine several tests of the same variable or expression into a single block of statements. The following shows the same example converted to use switch.

switch(button) {
    case "next":
        window.location="next.html";
        break;
    case "previous":
        window.location="prev.html";
        break;
case "home":
        window.location="home.html";
        break;
case "back":
        window.location="menu.html";
        break;
default:
        window.alert("Wrong button.");
}

The switch statement has several components:

• The initial switch statement. This statement includes the value to test (in this case, button) in parentheses.
• Braces ({ and }) enclose the contents of the switch statement, similar to a function or an if statement.
• One or more case statements. Each of these statements specifies a value to compare with the value specified in the switch statement. If the values match, the statements after the case statement are executed. Otherwise, the next case is tried.
• The break statement is used to end each case. This skips to the end of the switch. If break is not included, statements in multiple cases might be executed whether they match or not.
• Optionally, the default case can be included and followed by one or more statements that are executed if none of the other cases were matched.

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