Invokes functions that are given as arguments in succession. Works like flow/pipe/compose, but all functions are given an additional "state" argument which may contain any additional values that are needed by all functions e.g. configuration. Inspired by the Reader monad.

readerCompose.js

// Invokes functions that are given as arguments in succession.
// Works like flow/pipe/compose, but all functions are given an additional "state" argument 
// which may contain any additional values that are needed by all functions e.g. configuration.
// Inspired by the Reader monad.
const readerCompose = (functions) => functions
  .reduce((fn1, fn2) => (state) => (...args) => 
    fn2(state)(fn1(state)(...args))
  )

const state = {
  stateVal: 5,
}

const test = readerCompose([
  (state) => (val) => {
    console.log('input is now', val) // 1
    console.log('Value in state is', state.stateVal) // 5
    console.log('Adding one to input')
    return val + 1
  },
  (state) => (val) => {
    console.log('input is now ', val) // 2
    console.log('Value in state is still', state.stateVal) // 5
    return val
  }
])({stateVal: 5})

test(1)