defekt

defekt

defekt is custom errors made simple.

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Installation

$ npm install defekt

Quick start

First you need to add a reference to defekt in your application:

const { defekt } = require('defekt');

If you use TypeScript, use the following code instead:

import { defekt } from 'defekt';

Then call the defekt function and hand over an object of custom error configurations that you would like to have created. In this object each key is the name for an error and the corresponding value is the error's configuration.

const errors = defekt({
  ArgumentNull: {},
  InvalidOperation: {},
  // ...
});

The result is an object containing all the errors you specified. To use one of those errors, simply call the appropriate function with new and throw it:

throw new errors.InvalidOperation();

By default, the error name is also used as the error message, but converted to a human readable form. E.g., the error name InvalidOperation becomes the message Invalid operation.:

try {
  throw new errors.InvalidOperation();
} catch (ex) {
  console.log(ex.message);
  // => 'Invalid operation.'
}

If you want to specify a custom message, feel free to do so:

throw new errors.InvalidOperation('Something failed.');

Additionally, if an error was caused by another error, you can specify this error using the cause property:

throw new errors.InvalidOperation('Something failed.', {
  cause: new Error(...)
});

From time to time, you may need to provide additional data for an error. For this, you can use the data property:

throw new errors.InvalidOperation('Something failed.', {
  data: { ... }
});

The custom errors follow the same rules as the built-in ones, i.e. they have a name and a message property, they derive from Error and they can be recognized by the util.isError function.

Defining error codes

By default, each custom error uses its uppercased name with an E prefix as error code. E.g., an InvalidOperation error uses EINVALIDOPERATION as its code.

From time to time, you may want to provide custom error codes. For that specify a code property on the configuration object:

const errors = defekt({
  ArgumentNull: { code: 'ARGNULL' },
  InvalidOperation: { code: 'INVALOP' }
  // ...
});

Running the build

To build this module use roboter:

$ npx roboter