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. 

Noraml Javascript array doesn't have traverse method, so we need to bring immutable-ext.

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)

 

Here 'futurize' give us a easy way to wrap a function into a Task. We can do it manually as well:

/*const readFile = (filename, encode) => new Task((rej, res) => {    return fs.readFile(filename, encode, (err, content) => {        if (err) rej(err);        res(content);    });});*/const readFile = futurize(fs.readFile);