promises-flow

Promises flow control with dependencies

install

npm install promises-flow

Usage

const promisesFlow = require('promises-flow');

promisesFlow
  .run({
    main: Promise.result('Hello'),
    dependent: {
      deps: ['main'],
      cb ({ main }) {
        return main + ' world';
      }
    },
  })
  .then(({ main, dependent }) => {
    console.log(dependent); // Hello world
  })
  .catch(/*...*/);

API

promisesFlow
  .run(Object) -> Promise

Each property of object (Promises Object) passed to run method should be a Promise (flow executors) or an object with two properties:

{
  deps: Array<String>,
  cb: Function,
}

Strings in deps array define dependencies and properties of object that will be passed to cb function.

cb function can return static values or Promise instance.

In result .run() returns promise with resolved object which contains all promises object properties with result of execution.

Errors

.run() throws 3 errors which help to configure promisesFlow correctly:

• Empty deps[]
• Not existed dependency: 'depName'
• Recursive dependency: 'depName

Each error produced by promisesFlow wrapped to PromisesFlowError(propertyName) instance with property name of passed to .run() object where error happens.

Errors that throws by inner code will be also wrapped with PromisesFlowError(propertyName).

Example

promisesFlow
  .run({
    init: Promise.resolve(),
    someField: {
      deps: ['init'],
      cb ({ init }) {
        return init.value;
      },
    },
  })
  .catch((err) => {
    console.log(err);
    /*
    { PromisesFlowError(someField): TypeError: Cannot read property 'value' of undefined
        at cb (promises-error.js:15:20)
        at <anonymous>
        at process._tickCallback (internal/process/next_tick.js:169:7)
        at Function.Module.runMain (module.js:607:11)
        at startup (bootstrap_node.js:158:16)
        at bootstrap_node.js:575:3 name: 'PromisesFlowError(someField)' }
    */
  });