What are the best practices for JavaScript error handling?

I'm looking to start making my JavaScript a bit more error proof, and I'm finding plenty of documentation on using try, catch, finally, and throw, but I'm not finding a ton of advice from experts on when and where to throw errors.

• Should every piece of code be wrapped in a try/catch?
• Is there more advice like this on at what point errors ought to be caught?
• Are there disadvantages to raising errors instead of having code fail silently in production?
• This has been touched on on SO as far as implementations, but have server-logging JS errors an effective strategy?
• Anything else I ought to know, regarding trapping errors in my application?

I'm also completely game for hearing of books that have great chapters or in-depth explanations of error-handling. Eloquent JavaScript touches on the matter, but isn't very prescriptive or opinionated about the issue.

Thanks for any advice you can give!

Solution 1:

An immensely interesting set of slides on Enterprise JavaScript Error Handling can be found at https://web.archive.org/web/20140126104824/http://www.devhands.com/2008/10/javascript-error-handling-and-general-best-practices/

In short it summarizes:

1. Assume your code will fail
2. Log errors to the server
3. You, not the browser, handle errors
4. Identify where errors might occur
5. Throw your own errors
6. Distinguish fatal versus non-fatal errors
7. Provide a debug mode

The slides go into much more detail and most probably will give you some direction.

EDIT:

The presentation mentioned above can be found here: https://www.slideshare.net/nzakas/enterprise-javascript-error-handling-presentation

Solution 2:

Nicholas Zakas of Yahoo! fame did a talk on Enterprise Error Handling (slides) at Ajax Experience 2008, in which he proposed something like this:

function log(sev,msg) {
    var img = new Image();
    img.src = "log.php?sev=" +
        encodeURIComponent(sev) +
        "&msg=" + encodeURIComponent(msg);
}

// usage
log(1, "Something bad happened.")

// Auto-log uncaught JS errors
window.onerror = function(msg, url, line) {
    log(1, msg);
    return true;
}

A year later, Nicholas Zakas posted an update on his blog which included a clever pattern to inject error handling code automatically on your production environment (using aspect-oriented programming).

When you start logging window.error calls, you're going to notice two things:

1. If your site is fairly complex, you're going to log a lot of errors
2. You'll be seeing a bunch of useless "window.error in undefined:0" messages

Reducing the torrent of log entries is as simple as testing for severity and/or a random number before logging to the server:

function log(sev,msg) {
    if (Math.random() > 0.1) return; // only log some errors

    var img = new Image();
    img.src = "log.php?sev=" +
        encodeURIComponent(sev) +
        "&msg=" + encodeURIComponent(msg);
}

Handling the useless window.error in undefined:0 errors depends on your site architecture, but can try identifying all Ajax calls and throwing an exception when something fails (possibly returning a stack trace using stacktrace.js).