Promise with ES6 generator

promisified-generator.js

// https://www.promisejs.org/generators/
function async(makeGenerator) {
  return function () {
    var generator = makeGenerator.apply(this, arguments);

    function handle(result){
      if (result.done) return Promise.resolve(result.value);

      return Promise.resolve(result.value).then(function (res){
        return handle(generator.next(res));
      }, function (err){
        return handle(generator.throw(err));
      });
    }

    try {
      return handle(generator.next());
    } catch (ex) {
      return Promise.reject(ex);
    }
  }
}

runGenerator.js

// A better promisifiled generator runner
// Support yielding promises and generators, like co (https://www.npmjs.com/package/co)
function runGenerator (makeGenerator) {
  return function (thisArg, args) {
    var generator = makeGenerator.apply(thisArg, args)

    function handle (result, gen) {
      var value = result.value

      if (value != null) {
        if (value.constructor.name === 'GeneratorFunctionPrototype') {
          value = handle(value.next(), value)
        } else if (value.constructor.name === 'GeneratorFunction') {
          value = runGenerator(value)(thisArg, args)
        }
      }

      if (result.done) {
        return Promise.resolve(value)
      }

      return Promise.resolve(value).then(function (res) {
        return handle(gen.next(res), gen)
      }, function (err){
        return handle(gen.throw(err), gen)
      })
    }

    try {
      return handle(generator.next(), generator)
    } catch (ex) {
      return Promise.reject(ex)
    }
  }
}