lie.js v1.1.8

lie.js

Adds useful helper functions to javascript Promises

What problem does this solve?

It allows promises to have a predictable timeout behaviour. This allows you to call a service and only wait for a fixed amount of time before trying something else. The Javascript Promise API does not include any concept of timeout. This makes working within a limited time budget difficult. For example if you are building a service that needs to give a response in 5 seconds and needs to call multiple services, sometimes returning a default value (or an error message) is better than timing out.

It's the ability to fail in a controlled manner that gives a service resiliance. You can't prevent things outside your control from failing. You can gracefully cope with that failure.

npm install lie.js

yarn add lie.js

Currently these include:

orReject

Creates a promise that will timeout after a given interval with a fixed message. This is the value that will be used as the error.

Promise.race([yourPromise, orReject('bang', 1)])

orTimeout

Creates a promise with a default value after a timeout.

These are intended to be used with Promise.race

isThenable

Determines if a given object has then (and therefore could be awaited).

This was inspired by the default behaviour of Erlang/OTP.

Service calls have a default timeout. If you have a fixed time budget then the only way to enforce this is to timeout with either a failure or a default value.

Promise.race([yourPromise, orTimeout('bang', 1)])

This can be very useful in tests. If you make the timeout configurable and use 0 then you can replace the result of the promise with a fixed result.

This has now been moved to use Typescript

I am now experimenting with github actions.