@leismore/lmos-nodejs-lmerror NPM

lmos-nodejs-lmerror

An Error class for LMOS for Node.js project

Features

Error Message & Code
HTTP-Response Integration
Chained-Errors Support
Timestamp

Motivation

When I wrote my first commercial Node.js project in 2019, I had been struggling to design a general error-handling module with the standard JavaScript Error object.

Because in the widely-used ECMAScript 3, the standard Error object only supports a text error message. Meanwhile in a real world server-side environment, handling an error usually means:

Identifying the error by a error-message for human and a error-code for machine
Recording the whole related error chain, if necessary
Sending a proper HTTP response according to the error

To satisfy the requirement of Node.js environment, I have decided to introduce the LMError class to simplify and standardise the error-handling process in Node.js or other server-side JavaScript environments.

LMError class is extended from the standard Error class. By integrating with the support of error message & error code, HTTP response, and error chain, now all errors can be processed by one error-handler under a unified procedure.

Installation

npm install @leismore/lmos-nodejs-lmerror

Test

npm test

Build

npm run build

Example

import { LMError, LMErrorErr, LMErrorRes } from '@leismore/lmos-nodejs-lmerror';

let error:LMErrorErr = { message: 'an error message', code: 'error_code_1984' };

let response:LMErrorRes = {
    statusCode: '500',
    headers: {
        'Content-Type': 'text/html; charset=utf-8',
        'Content-Language': 'en-GB'
    },
    body: `<!DOCTYPE html>
           <html lang="en-GB">
             <head>
               <meta charset="UTF-8">
               <title>500 Internal Server Error</title>
             </head>
             <body>
               <h1>500 Internal Server Error</h1>
               <p>Don't cry over spilt milk</p>
             </body>
           </html>`
};

let previous = new Error('standard Error');

throw new LMError(error, response, previous);

LMError Class

Data Types

type LMErrorErr = {
  readonly message: string, // Message for human
  readonly code:    string  // Code for machine
};

type LMErrorRes = {                                     // HTTP response
  readonly statusCode:  string,                         // HTTP response status code
           headers?:   {readonly [key:string]: string}, // HTTP headers
           body?:       any                             // HTTP body
};

Properties

public readonly error:       LMErrorErr;
public readonly response?:   LMErrorRes;
public          previous?:   Error;
public          timestamp:   Date;

Methods

/**
 * 
 * @throws Error
 *   invalid_error_message
 *   invalid_error_code
 *   invalid_http_statusCode
 *   invalid_http_header
 *   invalid_http_body
 *   invalid_previous
 * 
 */
public constructor(error: LMErrorErr, response?: LMErrorRes, previous?: Error)


/**
 * 
 * @throws Error
 *   invalid_previous
 *   previous_exists
 * 
 */
public addPrevious(previous: Error):void


public toString(): string