await-handler-ts

Simple signature to ease the paid of catching errors using async/await. This module will allow a simple method of catching errors from an await handler without the need to wrap everything in try/catch blocks. This module is a Node.js only version based on await-to-js minus the typescript aspect. Credit for this module goes to Dima Grossman, as it was based off the code provided.

You continue to use async/await normally, except to wrap the function you are "awaiting", in this module to allow destructuring the returned array into variables. This is similar to the golang error handling syntax.

NOTE: This module works in Node 6+, but in order to use async/await, you need to use Node 8+ or compile with Babel.

THIS ADD SUPPORT FOR TYPESCRIPT OF THE AWAIT-HANDLER MADE BY KyleRoss

Install

Install via NPM:

npm i await-handler --save

Install via YARN:

yarn add await-handler

Usage

JS

const on = require('await-handler');

async function asyncFunctionExample() {
    let [err, result] = await on(myAsyncTask());
    if(err) {
        throw err;
    }
    
    // ... handle the result
    console.log(result);
}

ES import

import on from "await-handler";

TS

import on from "await-handler";
async function asyncFunctionExample() {
    let [err, result] = await on(myAsyncTask());
    if(err) {
        throw err;
    }
    
    // ... handle the result
    console.log(result);
}

// with errorProps
async function asyncFunctionExampleWithErrorProps() {
    let [err, result] = await on<{props: string}, string>(myAsyncTask(), {props: "hey"});
    if(err) {
        console.log(err.props); // "hey"
        throw err;
    }
    
    // ... handle the result
    console.log(result);
}

// You can defined the type of the error adn the data by doing: 
async function asyncFunctionExampleWithErrorPropsAndDataType() {
    // the error will be of type Error or MyCustomError
    // the data will be of type string
    let [err, result] = await on<Error | MyCustomError, string>(myAsyncTask());
    if(err) {
        throw err; // err instanceof Error || err instanceof MyCustomError
    }
    
    // ... handle the result
    console.log(result); // result instanceOf string
}

API

on(promise[, errorProps])

Type: Function

Adds handler to promise in order to return an array which can be destructured. Optionally add additional properties to the returned error by providing an Object to errorProps.

Argument	Required?	Type	Description
promise	Yes	Promise	Promise to wrap and return results for.
errorProps	No	Object	Optional object to append to the Error if one is thrown.

Generic

on<errorType, dataType>() {};

Examples:

async function basicExample() {
    let [err, result] = await on(myAsyncTask());
    if(err) throw err;
    
    // ... handle the result
    console.log(result);
}

async function errorPropsExample() {
    let [err, result] = await on(myAsyncTask(), { customMessage: 'Something failed!' });
    // With typescript
    let [err, result] = await on<{customMessage: string}>(myAsyncTask(), { customMessage: 'Something failed!' })
    if(err) {
        console.error(err.customMessage);
        return process.exit(1);
    }
    
    // ... handle the result
    console.log(result);
}

Returns {Promise<Array>}

Returns Promise that resolves with array signature [error, results]. If an error is thrown, error will be the the rejection from the promise and results will be undefined. If an error is not thrown, error will be null and results will be the resolved value from the promise.

---

Tests

To run the tests:

npm install
npm run test

License

MIT License. See License in the repository.