Javascript Error Handling Logging
Contents |
Web Dev @ Microsoft SEO By WooRank Books Courses Screencasts Newsletters Versioning Shop Forums Advertise Contribute Contact Us Our Story 995kSubscribers 132kFollowers 80kFollowers JavaScript Article A Guide
Exception Handling In Javascript Example
to Proper Error Handling in JavaScript By Camilo Reyes April 13, 2016 This article javascript error handling best practices was peer reviewed by Tim Severien and Moritz Kröger. Thanks to all of SitePoint's peer reviewers for making SitePoint content the best javascript global error handling it can be! Ah, the perils of error handling in JavaScript. If you believe Murphyʼs law, anything that can go wrong, will go wrong! In this article I would like to explore error handling in
Javascript Error Handling Library
JavaScript. I will cover pitfalls and good practices. We'll finish by looking at asynchronous code and Ajax. More from this author Saved from Callback HellQuick Tip: How to Throttle Scroll EventsGetting Started with the Raspberry Pi GPIO Pins in Node.js I feel JavaScriptʼs event-driven paradigm adds richness to the language. I like to imagine the browser as this event-driven machine, and errors are no different. When an error occurs, an event gets
Javascript Error Handling Tutorial
thrown at some point. In theory, one could argue errors are simple events in JavaScript. If this sounds foreign to you, buckle up as you are in for quite a ride. For this article, I will focus only on client-side JavaScript. This write up will build on concepts explained in the article Exceptional Exception Handling in JavaScript. To paraphrase: “with an exception JavaScript checks for exception handling up the call stack.” I recommend reading up on the basics if you are not familiar. My goal is to explore beyond the bare necessities for handling exceptions. The next time you see a nice try...catch block, it will make you think twice. The Demo The demo we'll be using for this article is available on GitHub, and presents a page like this: All buttons detonate a “bomb” when clicked. This bomb simulates an exception that gets thrown as a TypeError. Below is the definition of such a module with unit test. function error() { var foo = {}; return foo.bar(); } To begin, this function declares an empty empty object named foo. Note that bar() does not get a definition anywhere. Let’s verify that this will detonate a bomb with a nice unit test. it('throws a TypeError', function () { should.throws(target, TypeError); }); Thi
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us exception handling in javascript ppt Learn more about Stack Overflow the company Business Learn more about hiring developers
Javascript Catch Specific Exception
or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack javascript try without catch Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up How to log exceptions in JavaScript up vote https://www.sitepoint.com/proper-error-handling-javascript/ 5 down vote favorite 2 As a C# developer I'm used to the following style of exception handling: try { throw SomeException("hahahaha!"); } catch (Exception ex) { Log(ex.ToString()); } Output ------ SomeNamespace.SomeException: hahahaha! at ConsoleApplication1.Main() in ConsoleApplication1\Program.cs:line 27 Its really simple, and yet tells me everything I need to know about what the exception was and where it was. How do I achieve the equivalent thing in http://stackoverflow.com/questions/1238000/how-to-log-exceptions-in-javascript JavaScript where the exception object itself might just be a string. I really want to be able to know the exact line of code where the exception happened, however the following code doesn't log anything useful at all: try { var WshShell = new ActiveXObject("WScript.Shell"); return WshShell.RegRead("HKEY_LOCAL_MACHINE\\Some\\Invalid\\Location"); } catch (ex) { Log("Caught exception: " + ex); } Output ------ Caught exception: [object Error] EDIT (again): Just to clarify, this is for internal application that makes heavy use of JavaScript. I'm after a way of extracting useful information from JavaScript errors that may be caught in the production system - I already have a logging mechanism, just want a way of getting a sensible string to log. javascript exception-handling share|improve this question edited Sep 18 '09 at 15:56 community wiki 4 revsJustin add a comment| 7 Answers 7 active oldest votes up vote 0 down vote accepted You can use almost in the same manner ie. try { throw new Error("hahahaha!"); } catch (e) { alert(e.message) } But if you want to get line number and filename where error is thrown i suppose there is no crossbrowser solution. Message and name are the only standart properties of Error object.
to your server side log: When using a try-catch block to handle errors explicitly, as described here. When using window.onerror to handle JavaScript errors, as described on this page. window.onerror The window.onerror handler lets you handle http://jsnlog.com/Documentation/HowTo/JavascriptErrorHandling any JavaScript errors that haven't been caught elsewhere in your code. The JavaScript interpreter will pass your handler an error message, the url of the file where the javascript exception happened, and the line https://developer.mozilla.org/en-US/docs/Archive/Mozilla/Exception_logging_in_JavaScript number. On more modern browsers, you get the column number and exception as well. JSNLog sets a handler for uncaught JavaScript errors When it loads, the jsnlog.js library checks if window.onerror has been set. If error handling it isn't, it sets a handler that logs uncaught JavaScript errors to your server side log: // Code included in jsnlog.js to set a handler that logs uncaught JavaScript errors to // the server side log. if (window && !window.onerror) { window.onerror = function (errorMsg, url, lineNumber, column, errorObj) { JL("onerrorLogger").fatalException({ "msg": "Uncaught Exception", "errorMsg": errorMsg, "url": url, "line number": lineNumber, "column": column }, errorObj); return false; } } Looking javascript error handling at this code, you'll see that the browser is supposed to pass 5 parameters to the onerror handler. Unfortunately, not all browsers pass in all parameters. If there is an uncaught JavaScript error on a browser that doesn't support all 5 parameters, the missing parameters are left undefined. In that case, JSNLog will simply only send the parameters that it did get. This way, when more browsers start supporting the full set of parameters, you will get all the available information. You'll also notice that this code returns false. This tells the browser to do its own error handling in addition to the handler - so it will write a message to the console, etc. Returning true would have told the browser that the error has been completedly handled and it doesn't need to do anything. How to set your own handler for uncaught JavaScript errors To override JSNLog's handler, simply set window.onerror to your own handler. If your code runs before jsnlog.js loads, jsnlog.js will see that window.onerror has already been set and leave it alone. If your code runs after jsnlog.js loads, your code will overwrite window.onerror. How to prevent logging of uncaught JavaScript errors If you do not want to log uncaught JavaScript erro
References & Guides Learning web development Tutorials References Developer Guides Accessibility Game development ...more docs Mozilla Docs Add-ons Firefox Developer ToolsFeedback Get Firefox help Get web development help Join the MDN community Report a content problem Report a bug Search Search Archive of obsolete content Languages No translations exist for this article. Add a translation Edit Advanced Advanced History Print this article MDN Archive of obsolete content Archived Mozilla and build documentation Exception logging in JavaScript Your Search Results teoli savanna1004 kscarfone Wladimir_Palant Sevenspade Bent Sheppy Exception logging in JavaScript In This Article Exception reporting in Firefox 3Forcing logging of exceptions in inner JS framesSee also In versions of Firefox prior to Firefox 3, all JavaScript exceptions were always logged into the Error Console if they remained unhandled at the time execution returned back into C++ code. As a result, if, for example, C++ code called a JavaScript component, which threw an exception, that exception would be logged to the console before control was returned to the C++ caller. This had the unintended consequence of logging "expected" errors at length into the console. JavaScript code is sometimes designed to throw exceptions to report a result condition back to the C++ caller. These might be perfectly normal circumstances, but the exceptions were dutifully logged nonetheless. Exception reporting in Firefox 3 Firefox 3 improves reporting of unhandled exceptions by establishing a set of rules that determines whether or not an exception is worth reporting: Any methods on interfaces annotated with the [function] attribute in IDL (see, for example, nsIDomEventListener) that throw exceptions always report those exceptions into the Error Console. Any exceptions that are generated by XPConnect -- that is, those exceptions whose result codes are defined in nsIXPConnect.idl -- are always logged into the Error Console. The NS_NOINTERFACE error is never reported when returned by a JavaScript object's QueryInterface() method on the nsISupports interface. The NS_NOINTERFACE error is never reported when returned by a JavaScript object's GetInterface() method on the nsII