mapWhile - cancellable map function

mapwhile.js

import R from "ramda";

const mapWhile = R.curry((
  predicate, // while fn - receives current partial list & value, returns bool
  transformation, // map fn
  list // source list
) => R.reduce((oldAcc, oldVal) => {
  const newVal = transformation(oldVal);
  const newAcc = [ ...oldAcc, newVal ];
  return predicate(newAcc, newVal) ? newAcc : R.reduced(oldAcc);
}, [], list));


mapWhile(
  x => x.length < 5,
  x => x + 1,
  [0, 0, 0, 1, 0, 0]
);