text: 'use strict';
  var $ = require('../internals/export');
  var IS_PURE = require('../internals/is-pure');
  var getBuiltIn = require('../internals/get-built-in');
  var anObject = require('../internals/an-object');
  var aFunction = require('../internals/a-function');
  var speciesConstructor = require('../internals/species-constructor');
  var iterate = require('../internals/iterate');
  
  // `Set.prototype.union` method
  // https://github.com/tc39/proposal-set-methods
  $({ target: 'Set', proto: true, real: true, forced: IS_PURE }, {
    union: function union(iterable) {
      var set = anObject(this);
      var newSet = new (speciesConstructor(set, getBuiltIn('Set')))(set);
      iterate(iterable, aFunction(newSet.add), { that: newSet });
      return newSet;
    }
  });
  