Promise-chain

This lib aims to make a network of promises easily configurable. Rejection of a promise should not lead per se to an overall rejection, but you can define an "on reject" handler (another promise following in the "reject" case).

Terminology

• "chain" ... the chained promises
• "chain item" ... one promise plus its metadata for linking it within the chain

Basic Usage

Include the lib in your app:

const promiseChain = require('promise-chain');

You can switch on debugging output with:

const promiseChain = require('promise-chain');
promiseChain.setDeubg(true);

Specifying a promise chain

A "chain item" is nothing else than a promise returning function plus a couple of properties which define the chaining behavior.

Recognized properties are:

• promise ... {function} the promise returning function
• onResolve ... {ChainItem} the next chain item to be executed on success of the current item
• onReject ... {ChainItem} the next chain item to be executed if the current item rejects
• name ...{string} an identifier string. This is used a the key for the errors object
• setError ... {boolean} if set, a rejected promise will even be registered in the errors structure of the result object if it has an onReject successor. If false,a rejected promise with a onReject successor will not produce an error. A rejected promise without an onReject setting will always produce an error. Default is false.
• errorKey ... {string} (optional) if set then this key will be used in the errors objects. If this property is omitted, the property name will be used per default. This property should help you collecting possibly many promises in the chain into one error "candidate". For example, to populate input fields in a HTML form, it helps to assign several tests for one field to the one field name. In this case, you would set errorKey according to the name of the HTML form field while leaving name uniqu (for tracking and debugging purposes)

Returned result object:

• errors ... an object consisting of all error objects of the rejected promises. Key is the chain link name (property name) and value is the rejection value, whatever this is
• success ... an array listing all resolved promises