Have you come recently from Java or C# world into JavaScript and you start wondering how the hell we are living here with the basic Error constructor? Yea, our stack traces aren't well descriptive, BUT here it is - Exception class just for you! Dive deep into the Quick showcase and see how this little lib can significantly improve your stack traces today.

Tip of the day - If you are coding in TypeScript, remember to output source maps and also enable them in Node.

Table of contents

• Quick showcase
• Installation
• API
• Custom exceptions

Quick showcase

For those who don't like to read a lot.

Code

async function accessFileSystemFile() {
  // some neat code here...
  throw new Error('I/O Error');
}

async function readLatestLog() {
  try {
    // some neat code here...
    return await accessFileSystemFile();
  } catch(e: unknown) {
    throw new Exception('Unable to read log file.', e);
  }
}

async function bootstrap() {
  try {
    await readLatestLog();
  } catch (e: unknown) {
    throw new Exception('Failed to do some dangerous stuff.', e);
  }
}

void bootstrap();

Stack trace

Exception: Failed to do some dangerous stuff.
    at file:///path/to/project/src/real-world-example.js:26:19
    at Generator.throw (<anonymous>)
    at rejected (/path/to/project/node_modules/tslib/tslib.js:113:69)
Caused by: Exception: Unable to read log file.
    at file:///path/to/project/src/real-world-example.js:16:19
    at Generator.throw (<anonymous>)
    at rejected (/path/to/project/node_modules/tslib/tslib.js:113:69)
Caused by: Error: I/O Error
    at file:///path/to/project/src/real-world-example.js:6:15
    at Generator.next (<anonymous>)
    at /path/to/project/node_modules/tslib/tslib.js:115:75
    at new Promise (<anonymous>)
    at __awaiter (/path/to/project/node_modules/tslib/tslib.js:111:16)
    at accessFileSystemFile (file:///path/to/project/src/real-world-example.js:4:12)
    at file:///path/to/project/src/real-world-example.js:13:26
    at Generator.next (<anonymous>)
    at /path/to/project/node_modules/tslib/tslib.js:115:75
    at new Promise (<anonymous>)

Installation

npm install --save enhanced-exception

or

yarn add enhanced-exception

API

Exception class

| element | signature | comment | |-------------|----------------------------------------|--------------------------------------------------------------| | constructor | (message?: string, previous?: unknown) | Creates new Exception class object. | | .message | string | Exception message, the same as in classic Error object. | | .name | string | Exception class name, the same as in classic Error object. | | .previous | unknown | Previous error, provided via constructor. |

Custom exceptions

Thanks to the fact that PlayerNotFoundException class extends Exception class, it also inherits all it's capabilities.

class PlayerNotFoundException extends Exception {
  playerName: string;

  constructor(playerName: string, previous?: unknown) {
    super(`Player "${playerName}" not found.`, previous);
    this.playerName = playerName;
  }
}

try {
  // some neat code here...
  throw new Error('Database record not found');
} catch(e: unknown) {
  throw new PlayerNotFoundException('IdkMan2', e);
}

PlayerNotFoundException: Player "IdkMan2." not found.
    at file:///path/to/project/src/real-world-example.js:13:11
    at ModuleJob.run (node:internal/modules/esm/module_job:194:25)
Caused by: Error: Database record not found
    at file:///path/to/project/src/real-world-example.js:10:11
    at ModuleJob.run (node:internal/modules/esm/module_job:194:25) {
  playerName: 'Failed to do some dangerous stuff.'
}