stepp

Promise-compatiable Promise wrapper for controlling concurrency of promises.

• Quick Start
• API
• License

Quick Start

The idea is for step to be a drop-in replacement for your promises (in terms of syntax), but for the execution to be delayed. So you can create a step with a given job but it will not execute until you run step.run(). This can be used to "delay" execution (similar to wrapping a promise with a function) or more importantly, used to limit concurrency.

To limit concurrency while executing many steps, you can do something like this:

const Step = require('stepp')
const values = [... new Array(1000).keys()]

const steps = values.map(id => {
  return new Step((resolve, reject) => {
    resolve(id)
  })
})

// steps will be a list of steps where each step should resolve
// a different id from the list of values
// 
// `.all()` returns a promise, so you can use it as you would use
// `Promise.all()`.
Step.all(steps)
  .then(newValues => {
    // newValues is deep equal to values
    // not necessarily in the right order though - race conditions
    // and what not
  })

API

.all(steps, [options])

• steps (array of Steps): the steps to execute.
• options (object): configuration object with the following properties:
  • failFast (boolean; default: true):
    • if true, the all promise is rejected as soon as an error occurs.
    • if false, the all promise is rejected after running all the steps with an array of errors.
  • maxConcurrency (number): the maximum number of steps that can be run in parallel.

License

Licensed under MIT license.

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