text: 'use strict';
  // https://github.com/tc39/proposal-iterator-helpers
  var $ = require('../internals/export');
  var global = require('../internals/global');
  var call = require('../internals/function-call');
  var aCallable = require('../internals/a-callable');
  var anObject = require('../internals/an-object');
  var getBuiltIn = require('../internals/get-built-in');
  
  var Promise = getBuiltIn('Promise');
  var TypeError = global.TypeError;
  
  $({ target: 'AsyncIterator', proto: true, real: true, forced: true }, {
    reduce: function reduce(reducer /* , initialValue */) {
      var iterator = anObject(this);
      var next = aCallable(iterator.next);
      var noInitial = arguments.length < 2;
      var accumulator = noInitial ? undefined : arguments[1];
      aCallable(reducer);
  
      return new Promise(function (resolve, reject) {
        var loop = function () {
          try {
            Promise.resolve(anObject(call(next, iterator))).then(function (step) {
              try {
                if (anObject(step).done) {
                  noInitial ? reject(TypeError('Reduce of empty iterator with no initial value')) : resolve(accumulator);
                } else {
                  var value = step.value;
                  if (noInitial) {
                    noInitial = false;
                    accumulator = value;
                    loop();
                  } else {
                    Promise.resolve(reducer(accumulator, value)).then(function (result) {
                      accumulator = result;
                      loop();
                    }, reject);
                  }
                }
              } catch (err) { reject(err); }
            }, reject);
          } catch (error) { reject(error); }
        };
  
        loop();
      });
    }
  });
  