JValue TypeScript Error Handling

Note: This library is currently NOT in use and was replaced by @sniptt/monads which provides similar functionality.

A simple library for error handling, used in the JValue projects.

Examples

Results

Use ResultLike to express Success and Failure of an operation.

const s = success(123);
const f = failure('My custom failure message');

This enables error handling without try/catch.

const result = someOperationReturningAResultLike();
if (result.isSuccess()) {
	const data = result.data();
	// do sth with the data
} else {
	const errorMsgs = result.errors();
	// do sth with the error messages
}

All recoverable cases should be expressed explicitly as a ResultLike.

Options

Use OptionLike to express Some and None of a type.

const s = some(123);
const n = none();

This enables using syntactic sugar for default values.

const option = someOperationReturningAnOptionLike();
const result = option.orElse('Default value');

Mapping/Filtering

ResultLike and OptionLike both support the methods map, flatMap, and filter.

TODO

Install

• Download dependencies: npm install

Linting

• Linting: npm run lint

Testing

• One test run: npm test
• Start tests in watch mode: npm run test:watch

VSCode Setup

We propose to use the following VSCode plugin so benefit from our preset configs out of the box:

• ESLint: dbaeumer.vscode-eslint
• Prettier: esbenp.prettier-vscode
• Editorconfig: editorconfig.editorconfig

Config ESlint

Recommended config (paste into /.vscode/settings.json):

{
	"eslint.validate": ["typescript"],
	"typescript.preferences.importModuleSpecifier": "relative",
	"[javascript]": {
		"editor.formatOnSave": true,
		"editor.defaultFormatter": "esbenp.prettier-vscode"
	},
	"[json]": {
		"editor.formatOnSave": true,
		"editor.defaultFormatter": "esbenp.prettier-vscode"
	},
	"[jsonc]": {
		"editor.formatOnSave": true,
		"editor.defaultFormatter": "esbenp.prettier-vscode"
	},
	"[typescript]": {
		"editor.formatOnSave": false,
		"editor.defaultFormatter": "esbenp.prettier-vscode",
		"editor.codeActionsOnSave": ["source.fixAll.format", "source.fixAll.eslint"]
	}
}

License

Copyright 2022 Friedrich-Alexander University Erlangen-Nürnberg (FAU). This work (source code) is licensed under Apache-2.0.