Javascript Snippets

coroutine.js

// Turn a generator function into a coroutine
const coroutine = (f) => (...args) => {
  const g = f(...args) // instantiate the generator
  const iter = ({ done, value }) => done  // iterate over suspensions
    ? value
    : value.then(
      (d) => iter(g.next(d)),
      (e) => iter(g.throw(e))
    )
  return Promise.resolve().then(() => iter(g.next())) // start iterating asynchronously
}

curry.js

// Curry a function
const curry = (f) => f.length
  ? (a) => curry(f.bind(null, a))
  : f

const uncurry = (f) => (...args) => args.length
  ? uncurry(f(args[0]))(...args.slice(1))
  : f()

promisify.js

// Turn a Node.js style continuation function into a promise
const promisify = (f) => (...args) => 
  new Promise((resolve, reject) => f(...args, (err, d) => err != null ? reject(err) : resolve(d)))

// Turn a promise into a function that can be called with a Node.js style continuation function
const nodify = (p) => (cb) => p.then((d) => cb(null, d), cb)