Just a little POC of retry function.

README.md

Retry

A little POC of a retry function in JavaScript.

example.js

const retry = require('./retry')

function failNTimes(n) {
  let failed = 0
  return () => {
    if (failed < n) {
      ++failed
      throw new Error('failed')
    }
    return 'succeed'
  }
}

const singleFail = failNTimes(1)

retry(singleFail, 2)
  .then(res => console.assert(res === 'succeed'))
  .then(() => console.log('It should succeed after second attempt'))


const fail3Times = failNTimes(3)
retry(fail3Times, 3)
  .catch(err => console.assert(err.toString() === new Error('failed').toString()))
  .then(() => console.log('It should fail after third attempt'))


let invoked = false
retry(() => (invoked = true), 0)
  .then(() => console.assert(invoked === false))
  .then(console.log('It should not have been invoked'))

// let n = 0
// const r = retry(() => {
//   if (n < 3) {
//     n++
//     throw 'Error ' + n
//   }
//   return 'Success'
//   }, 4)
//   .then(res => console.log('res', res, n))
//   .catch(() => console.log('catch', n))

retry.js

module.exports = retry

function retry(fn, times, ...args) {
  if (times === 0) {
    return Promise.resolve()
  }

  return new Promise(resolve => {
    resolve(fn(...args))
  }).catch(err => {
    if (times > 1) {
      return retry(fn, times - 1, ...args)
    }
    return Promise.reject(err)
  })
}