core-js/modules/esnext.map.key-of.js

'use strict';
var $ = require('../internals/export');
var IS_PURE = require('../internals/is-pure');
var anObject = require('../internals/an-object');
var getMapIterator = require('../internals/get-map-iterator');
var iterate = require('../internals/iterate');

// `Map.prototype.includes` method
// https://github.com/tc39/proposal-collection-methods
$({ target: 'Map', proto: true, real: true, forced: IS_PURE }, {
  keyOf: function keyOf(searchElement) {
    return iterate(getMapIterator(anObject(this)), function (key, value) {
      if (value === searchElement) return iterate.stop(key);
    }, undefined, true, true).result;
  }
});