ok-value-error-reason

An elegant way to handle exceptions from both synchronous and asynchronous functions.

Usage

By wrapping a function call with over, you get an union types Over (ok-value-error-reason) that represents the result of a function call.

import {
	over, // stand for 'ok-value-error-reason'
} from "ok-value-error-reason";

let ans = fnLetCrash(arg1); // => crash

let ans = over(fnLetCrash, arg1); // => ans is an `Over` object

Over object is either a OKValue or ErrorReason object.

export type OKValue<V> = {
	ok: true;
	value: V;
};
export type ErrorReason<R> = {
	ok: false;
	reason: R;
};

export type OVER<V, E> = OKValue<V> | ErrorReason<E>;

You can use .ok property to narrow types.

// Wrap fnReturnNumber execution so that it will return an Over object.
let ans = over<typeof fnReturnNumber, "EMPTY" | "TOO_LONG">(
	fnReturnNumber,
	arg1,
);

if (ans.ok) {
	// `ans` is an OKValue object
	console.log(ans.value); // `.value` is number
} else {
	// `ans` is an ErrorReason object
	console.error(ans.reason); // `.reason` is "EMPTY" | "TOO_LONG"
}

over is also compatible with async functions.

// async
let asyncAns = await over<typeof asyncFnReturnNumber, "EMPTY" | "TOO_LONG">(
	asyncFnReturnNumber,
	arg1,
);