Handling asynchronous programming with Ramda

I know, the question is old. But ramda has some cool functions to compose Promise-returning functions: pipeP and composeP.

Also take a look into regular compose (pipe) and it's Kleisli implementation composeK (pipeK). They allow to work with algebraic structures like Future or Task, which look the same as Promise, but lazy-evaluated.

pipeP and composeP got deprecated.

Create pipeWithPromise which accepts an array of promises or functions.

var pipeWithPromise = R.pipeWith((fun, previousResult) => (previousResult && previousResult.then) ? previousResult.then(fun) : fun(previousResult));
var tasks = [/* sync func */ $ => $ + '1', /* async func */ async $ => await $ + '2'];
var result = await pipeWithPromise(tasks)('state');
// result = 'state12';

You can use Promise.resolve to "wrap" a value in a promise.

getSectionFromDataPromise :: obj -> promise
getSectionFromDataPromise = R.pipe(getSectionFromData , (val) => Promise.resolve(val))

This way you can promote (lift) any function that returns a normal value to a one that returns a promise.

Lifting is an essential concept in FP. You can view Array.map as a function that lifts a function that transforms a value to a function that transforms an array of values.

You can use Promise.all to write a function that compares promises and (for example) throws an error if they are not equal.

function promiseEquals (f1, f2) {
  return Promise.all([f1(), f2()]).then(function(vals) {
    if(!R.equals(vals[0], vals[1])) {throw "The values aren't equal"}
    return vals[0]
  })
}

Lastly you can combine the two:

promiseEquals(getSectionFromDataPromise, getSectionFromDb)
  .then(function(val){
    console.log(val)
  })
  .catch(function(val){console.log("Error "+val)})