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
    • Tools for Scripting
    • What Time is It?
    • Beginning the Script
    • Adding JavaScript Statements
    • Creating Output
    • Adding the Script to a Web Page
    • Testing the Script
    • Workshop: Hiding Scripts from Older Browsers
    • Summary
    • Q&A
    • Quiz
    • Exercises
  • 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
  • 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

Workshop: Hiding Scripts from Older Browsers

Since older browsers don't understand the <script> tag, they will not behave very well when they encounter a script in a Web page. In most cases, they will display the script in the middle of the page—probably not the effect you were looking for.

To avoid this, you can enclose the script within HTML comment tags. This tells older browsers to ignore the script completely. Newer browsers are smart enough to know that your script isn't really a comment.

HTML comments begin with the tag <!-- and end with the --> tag. Listing 2.4 shows a simple example of a script with comments.

Example 2.4. Hiding a script from older browsers

<SCRIPT LANGUAGE="JavaScript">
   <!--
   document.write("Your browser supports JavaScript.");
   // -->
</SCRIPT>

This script includes the beginning and ending HTML comment tags. The // in the last line is a JavaScript comment; this prevents the HTML comment from being detected as a JavaScript error.

Share This