April 2007
Intermediate to advanced
1728 pages
47h 51m
English
Content preview from JavaScript® Bible, Sixth EditionBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Chapter 45. Debugging Scripts
IN THIS CHAPTER
Identifying the type of error plaguing a script
Interpreting error messages
Preventing problems before they occur
One of the first questions that an experienced programmer asks about a programming environment is what support is there for debugging code. Even the best coders in the world make mistakes when they draft programs. Sometimes, the mistakes are a mere slip of a finger on the keyboard; other times, they result from not being careful with expression evaluation or object references. The cause of the mistake is not the issue: finding the mistake and getting help to fix it is.
Some debugging tools are available for the latest browsers. For the most part, they have come from the browser makers themselves, or they are tied very closely to a particular authoring environment. Some of these tools are very quirky; others require significant investments in authoring environments. Discussion about debugging tools in this chapter, however, focuses on simple tools you can download online. By understanding the true meaning of error messages and working out the problem with the tools provided here, you should be able to overcome your bugs.
Syntax versus Runtime Errors
As a page loads into a JavaScript-enabled browser, the browser attempts to create an object model out of the HTML and JavaScript code in the document. Some types of errors crop up at this point. These are mostly syntax errors, such as failing to include a closing brace after a function's ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.