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Mozilla (all platforms)

The problem with IE/Mac’s error alerts is that it doesn’t give an accurate line number for external scripts

(the line number is typically the line in the HTML file where the script has been referenced). In extreme

cases, it may be more useful to insert the script inline for testing purposes.

Mozilla features a JavaScript console that logs not only errors, but warnings as well. To access the

JavaScript console, look under Tools

Web Development

JavaScript Console in Mozilla 1.0+ (prior

to 1.0, the JavaScript console was located under Tasks

Tools

JavaScript Console).

Just like its predecessor Netscape Navigator, Mozilla allows you to type javascript: into the address

box to open the JavaScript console instead of accessing it from the menu.

The JavaScript console reports three types of messages: errors, strict warnings, and messages. Errors are

either syntax or runtime errors (anything that stops script execution), and they are reported with the

error message, the filename, and the line number on which the error occurred (Figure 14-5). Strict warn-

ings occur when the code does something illegal, but the interpreter works around it allowing the script

to continue running (such problems include redefining a previously defined variable). Messages are

purely informational and often are a result of internal Mozilla processing, not JavaScript.

Figure 14-5

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