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Javascript Error Class

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If you need additional methods/properties, you can add them to the object before returning it. c) Because the solution at https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error does not seems to preserve stack info. //MyError class constructor function MyError(msg){ this.__proto__.__proto__ = Error.apply(null, arguments); }; usage example http://jsfiddle.net/luciotato/xXyeB/ What does it do? Otherwise, the exception is rethrown. Don't swallow the exception until you really sure try { func() } catch(e) { if (e instanceof KnownError) { // ... } } In the snippet above, other exception types except Source

javascript exception error-handling share|improve this question edited Apr 19 '11 at 1:56 asked Sep 5 '09 at 0:54 Josh Gibson 6,052154960 20 I know it's been awhile, but can you Periodically, I see people throwing errors by just providing the string, such as this: throw "message"; Doing so will cause an error to be thrown, but not all browsers respond the message: A description of the error, with this description varying depending on the browser. westy92 commented Jul 30, 2016 • edited I'm using TypeScript and came up with the following solution: class MyError extends Error { static name: string; constructor(public message?: string, public extra?: number) her latest blog

Javascript Error Message

I find it helps me to track down issues -- post-mortem -- but also to clearly handle expected errors. IE users would probably never notice, but users of Fire Bug on FF will see useless file name and line number values reported alongside these Errors, and will have to drill The syntax is: throw myerrorobject Where myerrorobject can in fact be anything from a string, number, Boolean, to a new or one of the 6 default Error Constructor functions.

It's argument e is assigned to a special exception object which contains the information about what happened. What myerrorobject is set to mainly just affects what error.name and error.message returns in your catch clause. lineNumber Optional. Nodejs Throw Error Here is an example using getters (IE9): function MyError(wrapped) { this.wrapped = wrapped; this.wrapped.name = 'MyError'; } function wrap(attr) { Object.defineProperty(MyError.prototype, attr, { get: function() { return this.wrapped[attr]; } }); }

You can also use if (err instanceof SpecificError) to add your own context specific error handling code. Javascript Throw Exception Typically, these are operational errors that occur when an application violates an operating system constraint such as attempting to read a file that does not exist or when the user does Clearly, this is suboptimal from a debugging point of view. thats really important to do.. –B T Jul 30 '13 at 0:07 Updated to include message, thanks. –sinisterchipmunk Aug 10 '13 at 0:50 add a comment| up vote 3

Properties Error.prototype Allows the addition of properties to Error instances. What Is Error Please contact webmaster" } And with that we throw in the towel! catch statements .. } finally { .. Designing Error Objects Once you start subclassing Error and adding your own properties, you can cause new problems by breaking the SOLID principles.

Javascript Throw Exception

Error.captureStackTrace(targetObject[, constructorOpt])# Creates a .stack property on targetObject, which when accessed returns a string representing the location in the code at which Error.captureStackTrace() was called. http://www.javascriptkit.com/javatutors/trycatch2.shtml The error-checking way: Without exceptions, the validator could return either true or false. Javascript Error Message Throwing and Catching Errors You might have noticed I've been quiet about throw, and that's because we hardly ever use it anymore. Node Custom Error I'm hoping it might fix the stack-trace problem as well. –Gili Aug 2 '13 at 16:23 8 Simple trick to get meaningful stacktrace is to generate error in constructor and

Zakas and do not, in any way, reflect those of my employer, my colleagues, Wrox Publishing, O'Reilly Publishing, or anyone else. http://wirelessready.org/javascript-error/javascript-error.html What is this aircraft with elaborate folding wings? B. console.error(err); }); connection.pipe(process.stdout); A handful of typically asynchronous methods in the Node.js API may still use the throw mechanism to raise exceptions that must be handled using try / catch. Node Error Object

If something goes wrong, we'll see what is it in the catch section. Themes Podcast Forums Premium HTML & CSS JavaScript PHP Ruby Mobile Design & UX Entrepreneur Web WordPress Java Web Dev @ Microsoft SEO By WooRank × HTML & CSS JavaScript PHP It would give proper call stack + 1 line for constructor (it's a suitable pay-off): this.stack = new Error().stack; –Meredian Sep 20 '13 at 7:35 | show 16 more comments up have a peek here try { throw 5 } catch(e) { alert("Caught: "+e) } A validator example For example, let's write an age validator.

share|improve this answer answered Aug 19 '12 at 21:09 Augustus Kling 2,3271019 add a comment| up vote 0 down vote At the expense of not being able to use instanceof, the Es6 Extend Error A workaround I use is: function MyError(message, fileName, lineNumber) { var err = new Error(); if (err.stack) { // remove one stack level: if (typeof(Components) != 'undefined') { // Mozilla: this.stack Object.defineProperties(CustomError.prototype, { //fixes the link to the constructor (ES5) "constructor": setDescriptor(CustomError), "name": setDescriptor("JSU Error") }); function setDescriptor(value) { return { configurable: false, enumerable: false, writable: false, value: value }; } //returns

So, what to do in case when the variable may be undefined?

Of course, you can throw any type of data that you'd like. error.errno# Returns a number corresponding to the negated error code, which may be referenced in man 2 intro. This page documents the use of the Error object itself and its use as a constructor function. Javascript Custom Error Es6 Overrides the Object.prototype.toSource() method.

Any idea whether there's an easy way to fix that? If, for example, execution synchronously passes through a C++ addon function called cheetahify, which itself calls a JavaScript function, the frame representing the cheetahify call will not be present in the Define The decorator takes a name for the error type, and returns a function that takes an error message, and encloses the error name. Check This Out asked 7 years ago viewed 68229 times active 1 month ago Visit Chat Linked 1 How to throw error properly for a missing property? 209 What's a good way to extend

If V8 cannot determine a name for the function, only location information will be displayed for that frame. You should also create errors in logical places. To review, the basic syntax is: throw new Error("message"); This works in all browsers and will display the error information in the same way it would any unintentional JavaScript error. This site is not affiliated with Oracle corp.

Now let's go further and add other statements into try section. If you haven’t previously confirmed a subscription to a Mozilla-related newsletter you may have to do so. I find I hardly ever need to use throw. Error is avoided altogether because "exceptions are bad".

It is possible to omit catch if finally is provided: // rarely used, but valid try { .. } finally { .. } try..catch..finally and return The finally works in any Reload to refresh your session. It's hard to do it properly in every browser. Your own exceptions may have additional properties like extra or cause. ‹ Early and Late Binding Date/Time functions › Tutorial JavaScript: from the Ground to ClosuresJavascript and related technologiesOverview: JavaScript, Flash,

And here the try..catch construct kicks in. share|improve this answer answered Jul 23 '10 at 14:20 Blaine 1,1741011 Did I get it right - that if you do not subclass and use new Error(...) directly, then There's only going to be one catch block. more stack exchange communities company blog Stack Exchange Inbox Reputation and Badges sign up log in tour help Tour Start here for a quick overview of the site Help Center Detailed

This is great for creating your own definitions of what an error is and when control should be transferred to catch. All error types inherit from Error so checking the type with instanceof Error doesn't give you any useful information. Following the Liskov substitution principle also helps create maintainable error handling code. netmikey commented Jan 27, 2016 I'm using Visual Studio Code and am getting a Warning when creating the Error with new: Only a void function can be called with the 'new'

This answer probably needs some improvement when I get a chance. –George Bailey Nov 21 '13 at 13:29 | show 7 more comments up vote 31 down vote In ES6: class Custom exception objects should inherit from the existing "Error" types. Subclassing Error Subclassing errors is easy with Object.create or util.inherits (in Node).