@ehwillows/results

General error handling utilities.

Documentation

Utilities for handling errors. There are two major components:

• ResultContainer is a data structure for representing the result of process, usually a function return value or data returned from an API.
• GeneralError is a class for representing errors from various sources to a single data structure.

ResultContainer

A result container has a success field that is always either true or false. If it is true, then there will be a data filed with the return value. If it is false, there will be an errors filed which is an array of GeneralErrors. This structure is defined in TypeScript as a generic discriminated union so it is type aware. I strongly recommend enabling strict mode in TypeScript in order to use this structure ergonomically.

In addition to the ResultContainer structure there are a number of helper functions that make it easy to create and work with ResultContainers.

Try-Catch

try {
   const data = JSON.parse(jsonText)

   return success(data);
} catch (error) {
   return failure(fromNativeError(error));
}

Fetch Request

/**
* Makes a request to the API at the provided url and translates it to js data.
* @param url the url to fetch.
* @returns A ResultContainer with the returned data or errors.
*/
const getData = async (
   url: string
): Promise<ResultContainer<unknown>> => {
   const response = await fetch(url);

   if(response.ok) {
       // If response has an "ok" status code we will try to parse it as JSON.
       try {
           const data: unknown = await response.json();

           // If the response is successfully parsed, we return an error result who's `success` field
           // is true and the data is an unknown value that the API returned.
           return success(data);
       } catch(error) {

           // If the request fails to parse, we catch the returned Error and convert it to a
           // GeneralError then return a failure.
           return failure(fromNativeError(error, url))
       }
   } else {
       // If the Response is not "ok" then we convert it to a GeneralError and return the failure.
       return failure(fromResponse(response));
   }
}

GeneralError

The GeneralError class is meant to store data related to errors that developers typically need.