Safe function callbacks

Wraps a function in a domain to capture async errors.

Although domain is a deprecated API in node, it is sometimes the best option to solve specific problems trying to catch asynchronous errors. For those specific cases, this module comes to the rescue by easily wrapping a function call in a domain and forcing the callback to be called with the error instead of the uncaught error bubbling up and killing the whole process!

More information on deprecation status:

• https://nodejs.org/api/domain.html
• https://github.com/nodejs/node/issues/66

Install

npm install domain-wrap

Usage

Given a fn that uses the node-style callbacks, expecting a callback as the last parameter and this callback expecting an err as the first parameter, you can obtain a new function that will always call the callback and never throw an error:

const protect = require('domain-wrap')

function fn(argument, callback) {
  // would throw but in other tick related to this function as a consequence of
  // an async call, setTimeout, or similar
}

const protectedFn = protect(fn)
protectedFn(args, function (err, result) {
  // if `fn` throws, `err` will contain the thrown error
})

On the other hand, if fn returns a promise instead of accepting a callback, you can obtain and execute a new function that will always resolve or reject and never throw an error:

const protectAsync = require('domain-wrap').async

function fn(argument) {
  // would throw but in other tick related to this function as a consequence of
  // an async call, setTimeout, or similar
}

const protectedFn = protectAsync(fn)
protectedFn(args).catch(function (err) {
  // if `fn` throws instead of reject, `err` will contain the thrown error
})

API

protect(fn)

Parameters

• fn is a function that receives a callback as the last argument. The callback will receive an err object as the first argument.

Returns value

A new function that wraps fn and makes it safe to call.

protect.async(fn)

Parameters

• fn is a function that returns a Promise.

Returns value

A new function that wraps fn and makes it safe to call.

License

WTFPL