Exercise : Buggy Javascript

The following pages have mistakes that cause their JavaScript code not to work properly. Look at the pages, find the bug(s), and correct the problems.

1. buggy page #1 (JavaScript)
2. buggy page #2 (JavaScript)
3. buggy page #3 (JavaScript)
4. buggy page #4 (JavaScript)

Exercise Solution

• buggy1: HTML script tag has name of JS file misspelled. Discover by putting alert at top of JS file, noticing that it doesn't show, checking script tag.
• buggy2: HTML script tag is self-closing (not valid; breaks whole page in FF), and misspelled name of onclick attribute. Discover by using W3C HTML Validator.

Exercise Solution

• buggy3: many syntax errors:

  • semicolon after () in function header
  • '' instead of " to close string
  • Alert shouldn't be uppercase
  • ) instead of } to close function

  Discover by looking at Firebug error console, and/or by running JSLint.

• buggy4: syntax error, missing } brace. Discover by running JSLint (error message more helpful than Firebug's).