Erresult

This library aims to provide Rust like error handling in typescript.

Error handling

In many languages errors are Values, in rust this is implemented using the Result enum, sadly typescript doesn't provide enums that are powerful enough.

Here is a real code example:

Rust

fn main() {
    let number_str = "42";

    // convert the string to a number (i32 is a number)
    match number_str.parse::<i32>() {
        // Valid case
        Ok(num) => println!("Parsed number: {}", num),
        // Error case
        Err(err) => eprintln!("Error: {}", err),
    }
}

JavaScript

In JavaScript you surely know the try catch control flow, but it has multiple flaws:

• It doesn't force you to address potential errors
• It doesn't even provide you with the info that an error could be thrown
• It creates a new scope
• As [anything can be thrown](https://kentcdodds.com/blog/get-a-catch-block-error-message-with-typescr ipt) in JavaScript the cached error may not be an error at all
  • There is basically no Type safety

Using Erresult error management looks more like this:

import { result } from "erresult";

const numberStr = "42";

enum Error {
	NotANumber,
	TooBig,
	TooSmall,
}

result<number, Error>((Ok, Err) => {
	const number = parseInt(numberStr);

	if (isNaN(number)) return Err(Error.NotANumber)
	if (number > 1_000_000) return Err(Error.TooBig)
	if (number < 0) return Err(Error.TooSmall)

	return Ok(number)
}).match(
	(value) => console.log(`The parsed number is ${value}`),
	(err) => console.error(`The function returned an error: ${err}`),
	(msg) => console.log(`A error was thrown: ${msg}`)
)

See example.ts for the example above

Documentation

Documentation is available here.