Javascript create custom error object

The message property combined with the name property is used by the Error. toString( ) method to. Throwing a custom error. Test cases I used can be found here: JavaScript self- made Error object comparison. For example, let' s suppose you want to create a custom error class that takes an error code as the first argument and the error message as the second. function CustomError( message) { this. name = ' CustomError' ; this. message = message | | ' ' ; var error = new Error( this. message) ; error. stack; } CustomError. prototype = Object. prototype) ; try { throw. Error オブジェクトは、 ユーザー定義の例外の基底オブジェクトとして使用することもでき ます。. JavaScript には、 一般的な Error コンストラクタの他に、 中核となる 6 つの エラーコンストラクターがあります。. Error) ; CustomError.

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    Javascript object error

    prototype) ; CustomError. name = " CustomError" ;. js you can create a custom error like this: var util = require( ' util' ) ; function MyError( message) { this. message = message; Error. captureStackTrace( this, MyError) ; } util. inherits( MyError, Error) ; MyError. This is important as one of the core ideas of a language that can throw an exception is to allow custom Errors. Custom Error pattern. class MyError { constructor( message) { this. name = ' MyError' ; this. message = message; this. stack = new Error( ). stack; / / Optional } } MyError. class ExtendableError extends Error { constructor( message) { super ( message) ; Object.

    But it' s a bit tricky to correctly create a custom error class in Node. js, so here is an example. The example also shows. you should avoid. call( this) - creates another error object ( wasting a bunch of time) and doesn' t touch this at all; Error. A few years ago I gave a talk at MountainWest JS called Error Handling in node. In that talk I extolled the virtues of creating custom error objects by extending the built- in Error type. The idea here is that we can create a special ServerError class which can take all of the data from the bad server response. JavaScript allows to use throw with any argument, so technically our custom error classes don' t need to inherit from Error. But if we inherit, then it becomes possible to use obj instanceof Error to identify error objects.

    So it' s better to inherit from. We' ll call it ValidationError and create a class for it. An error of that kind should. Can I define custom types for user- defined exceptions in JavaScript? Here is how you can create custom errors with completely identical to native Error ' s behaviour. getPrototypeOf( this) ) ; return instance; } CustomError. prototype, { constructor: { value: Error, enumerable: false, writable:.