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Custom Error Objects In Node.js With Error.captureStackTrace() By Ben Nadel on May 5, 2015 Tags: Javascript / DHTML Coming node.js create error object from the world of ColdFusion, I'm used to using the CFThrow node js custom error tag (and throw() function), which allows me to throw error objects with a good deal of
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contextual information that can later be used for debugging purposes. As such, I wanted to see if I could create a custom Error class in my Node.js code
Es6 Custom Error
that would mimic [some of] the properties available on the ColdFusion error object.As I've been digging around though lots of example Node.js code, I've seen two different approaches to this problem: Create many Error sub-classes, one for each type of error. And, creating one type of flexible error sub-class. Personally, I don't see the value error.capturestacktrace mdn in having lots of different types of error objects - JavaScript, as a language, doesn't seem to cater to Constructor-based error-catching. As such, differentiating on an object property seems far easier than differentiating on a Constructor type.Furthermore, with CFThrow, I'm used to differentiating based on the Type property; so, that's what I'll be exploring here, in a Node.js context.In addition to custom error properties (such as message and detail), the real focal point of the error object is the stacktrace. In the V8 engine, the stacktrace of an error is gathered using the Error.captureStackTrace() method:Error.captureStackTrace( errorObject, localContextFunction )This method injects a "stack" property into the first argument and, optionally, excludes the localContextFunction from the stacktrace. So, for example, if we were to generate the stacktrace inside of an error Factory function, we could tell V8 to exclude the factory function when generating the stack. This would reduce the noise of the error implementation and confine the stacktrace to meaningful information about the
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from subfuzion/error.md Last active Oct 21, 2016 Embed What would you node assert like to do? Embed Embed this gist in your website. Embed Share Copy sharable URL for this es6 extend error gist. Share Clone via HTTPS Clone with Git or checkout with SVN using the repository's web address. HTTPS Learn more about clone URLs Download ZIP Code Revisions 7 https://www.bennadel.com/blog/2828-creating-custom-error-objects-in-node-js-with-error-capturestacktrace.htm Stars 154 Forks 23 Creating custom Error classes in Node.js Raw custom-error.js 'use strict'; module.exports = function CustomError(message, extra) { Error.captureStackTrace(this, this.constructor); this.name = this.constructor.name; this.message = message; this.extra = extra; }; require('util').inherits(module.exports, Error); Raw error.md It's nice to be able to distinguish error types by classes. But it's a bit tricky to correctly create a https://gist.github.com/justmoon/15511f92e5216fa2624b custom error class in Node.js, so here is an example. The example also shows how to add an extra parameter called extra that will be stored as a property on the error. Usage var CustomError = require('./errors/custom-error'); function doSomethingBad() { throw new CustomError('It went bad!', 42); } Features Name appears once - less editing if you have to create lots of custom error classes Easy to subclass - just change the last line to inherit from another custom error class you created Correct stack trace - no extra stack frames, no double capturing of the stack trace Anti-patterns These are some things that I've seen in other proposed solutions that you should avoid. Error.call(this) - creates another error object (wasting a bunch of time) and doesn't touch this at all Error.captureStackTrace(this, arguments.callee); - works, but arguments.callee is deprecated, so don't use it this.stack = (new Error).stack - this... I don't even... Raw test-error.js // Mini test suite for our custom error var assert = require('assert'); var Cus
Query Strings Readline REPL Stream String Decoder Timers TLS/SSL TTY UDP/Datagram URL Utilities V8 VM ZLIB GitHub Repo & Issue Tracker Mailing List Node.js v6.9.1 Documentation Index | View on single page | https://nodejs.org/api/errors.html View as JSON Table of Contents Errors Error Propagation and Interception Node.js style callbacks https://www.joyent.com/node-js/production/design/errors Class: Error new Error(message) Error.captureStackTrace(targetObject[, constructorOpt]) Error.stackTraceLimit error.message error.stack Class: RangeError Class: ReferenceError Class: SyntaxError Class: TypeError Exceptions vs. Errors System Errors Class: System Error error.code error.errno error.syscall Common System Errors Errors# Applications running in Node.js will generally experience four categories of errors: Standard JavaScript errors such as:
About Blog Sign In Free Trial Production Practices Joyent Node.js Production Practices Design Error Handling Design EventEmitter Streams Control Flow Coding Style Linting Logging Client Server Specific Software Error Handling Deploy Cluster Domains Deploying New Versions Service Management Dependency Management Debug Debugging Performance Issues Debug a Running Process (DTrace) Postmortem Postmortem Debugging with mdb Logging MDB Modules Share: Error Handling in Node.js Error handling is a pain, and it's easy to get by for a long time in Node.js without dealing with many errors correctly. But building robust Node.js apps requires dealing properly with errors, and it's not hard to learn how. If you're really impatient, skip down to the "Summary" section for a tl;dr. This document will answer several questions that programmers new to Node.js often ask: In functions that I write, when should I throw an error, and when should I emit it with a callback, event emitter, or something else? What should my functions assume about their arguments? Should I check that they're the correct types? Should I check more specific constraints, like that an argument is non-null, is non-negative, looks like an IP address, or the like? How should I deal with arguments that don't match what the function expects? Should I throw an exception or emit an error to the callback? How can I programmatically distinguish between different kinds of errors (e.g., a "Bad Request" error vs. a "Service Unavailable" error)? How can I provide enough detail with my errors so that callers can know what to do about them? How should I handle unexpected errors? Should I use try/catch, domains, or something else? This document is divided into several parts that build on one another: Background: what you're expected to know already. Operational errors vs. programmer errors: introduction to two fundamentally different kinds of errors Patterns for writing functions: general principles for writing functions that produce useful errors Specific recommendations for writing new functions: a checklist of specific guidelines for writing robust functions that produce useful errors An example: example documentation and preamble for a connect function Summary: a summary of everything up to this point Appendix: Conventional properties for Error objects: a list of p