[Compose] 19. Leapfrogging types with Traversable

We use the traversable instance on List to reimplement Promise.all() type functionality.

For example we want to conver:

[Task] => Task([])

Conver array of Task, into Task of array value.

To do that we can use traverse.

const fs = require(‘fs‘)
const Task = require(‘data.task‘)
const futurize = require(‘futurize‘).futurize(Task)
const { List } = require(‘immutable-ext‘)

const readFile = futurize(fs.readFile)

const files = List([‘box.js‘, ‘config.json‘])

files.traverse(Task.of, fn => readFile(fn, ‘utf-8‘))
.fork(console.error, console.log)