Generatorのプロトタイプ拡張。ま、やっつけです。

extendGeneratorPrototype.js

/* Usage
function * gene() {
  console.log("iter");
  yield 1;
  console.log("iter");
  yield 2;
  console.log("iter");
  yield 3;
}
var result = gene
  .filter(num => {
    console.log("filter: ", num);
    return num % 2 === 1;
  })
  .map(num => {
    console.log("map: ", num);
    return num + 10;
  });
console.log("result: ", [...result])
 */

{
  let g = function*(){};
  let GeneratorFunctionPrototype = g.constructor.prototype;
  let GeneratorPrototype = GeneratorFunctionPrototype.prototype;
  function reduceIter(iter, func, initValue) {
    let result = initValue, done, value;
    if (result === undefined) {
      let {done,value} = iter.next();
      if (done) return;
      result = value;
    }
    while({done, value} = iter.next(), !done) {
      result = func(result, value);
    }
    return result;
  }
  function * mapIter(iter, func) {
    let i = 0;
    for (let item of iter) {
      yield func(item, i);
      ++i;
    }
  }
  function * filterIter(iter, func) {
    let i = 0;
    for (let item of iter) {
      if (func(item, i)) yield item;
      ++i;
    }
  }
  function forEachIter(iter, func) {
    let i = 0;
    for (let item of iter) {
      func(item, i);
    }
  }
  Object.defineProperties(GeneratorFunctionPrototype, {
    reduce: {
      writable: true, configurable: true,
      value: function reduce (func, initValue) { return reduceIter(this(), func, initValue); }
    },
    map: {
      writable: true, configurable: true,
      * value(func) { yield * mapIter(this(), func); }
    },
    filter: {
      writable: true, configurable: true,
      * value(func) { yield * filterIter(this(), func); }
    },
    forEach: {
      writable: true, configurable: true,
      value(func) { forEachIter(this(), func); }
    }
  });
  Object.defineProperties(GeneratorPrototype, {
    reduce: {
      writable: true, configurable: true,
      value(func, initValue) { return reduceIter(this, func, initValue); }
    },
    map: {
      writable: true, configurable: true,
      * value(func) { yield * mapIter(this, func); }
    },
    filter: {
      writable: true, configurable: true,
      * value(func) { yield * filterIter(this, func); }
    },
    forEach: {
      writable: true, configurable: true,
      value(func) { forEachIter(this, func); }
    }
  })
}