euler2 with generators and shitty transducers

gistfile1.js

/** @jsx React.DOM */

// EULER 2

var isEven = val => val % 2 === 0;

var concat = (acc, cur) => acc.concat(cur)

var sum = (a, b) => a + b;

function* fibonacci() {
    var [prev, curr] = [1, 0]
    while (prev+curr < 4000000) {
        [prev, curr] = [curr, prev + curr];
        yield curr;
    }
}

function reduceSeqInto(seq, reducer, acc) {
  for (var x of seq) acc = reducer(acc, x);
  return acc
}

function filtering(pred) {
  return function(step) {
    return function(acc, cur) {
      return (pred(cur) ? acc : step(acc, cur))
    }
  }
}

var fibs = reduceSeqInto(fibonacci(), concat, Im.Vector())

var evenFibs = fibs.reduce(filtering(isEven)(sum), 0)