transducers.js

console.log([0, 1, 2, 3, 4, 5, 6, 7, 8, 9].map((x) => x + 1));
console.log([1, 2, 4, 5, 6, 7, 7, 8, 9, 10].filter((x) => x % 2 === 0));

console.log([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
  .map((x) => x + 1)
  .filter((x) => x % 2 === 0));

const mapIncReducer = (result, input) => result.concat(input + 1);
console.log([0, 1, 2, 3, 4, 5, 6, 7, 8, 9].reduce(mapIncReducer, []));

const mapReducer = (f) => (result, input) => result.concat(f(input));
console.log([0, 1, 2, 3, 4, 5, 6, 7, 8, 9].reduce(mapReducer((x) => x + 1), []));


console.log([0, 1, 2, 3, 4, 5, 6, 7, 8, 9].reduce(mapReducer((x) => x - 1), []));

console.log([0, 1, 2, 3, 4, 5, 6, 7, 8, 9].reduce(mapReducer((x) => x * x), []));

const filterEvenReducer = (result, input) => input % 2 === 0 ? result.concat(input) : result;

console.log([1, 2, 3, 4, 5, 6, 7, 8, 9, 10].reduce(filterEvenReducer, []));

const filterReducer = (predicate) => (result, input) => predicate(input) ? result.concat(input) : result;

console.log([1, 2, 3, 4, 5, 6, 7, 8, 9, 10].reduce(filterReducer((x) => x % 2 === 0), []));

console.log([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
    .reduce(mapReducer((x) => x + 1), [])
    .reduce(filterReducer((x) => x % 2 === 0), []));

console.log([1, 2, 3].concat(4));

console.log(10 + 1);

// result -> input -> result
const mapping = (f) => (reducing) => (result, input) => reducing(result, f(input));
const filtering = (predicate) => (reducing) => (result, input) => predicate(input) ? reducing(result, input) : result;

console.log([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
  .reduce(mapping((x) => x + 1)((xs, x) => xs.concat(x)), [])
  .reduce(filtering((x) => x % 2 === 0)((xs, x) => xs.concat(x)), []));

console.log(mapping((x) => x + 1)((xs, x) => xs.concat(x))([], 1));
console.log(mapping((x) => x + 1)((xs, x) => xs.concat(x))([2], 2));
console.log(mapping((x) => x + 1)((xs, x) => xs.concat(x))([2, 3], 3));
console.log(filtering((x) => x % 2 === 0)((xs, x) => xs.concat(x))([2, 4], 5));
console.log(filtering((x) => x % 2 === 0)((xs, x) => xs.concat(x))([2, 4], 6));

console.log([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
  .reduce(mapping((x) => x + 1)(filtering((x) => x % 2 === 0)((xs, x) => xs.concat(x))),
      []));