--- /dev/null
+'use strict';
+var $ = require('../internals/export');
+var IS_PURE = require('../internals/is-pure');
+var anObject = require('../internals/an-object');
+var bind = require('../internals/function-bind-context');
+var getMapIterator = require('../internals/get-map-iterator');
+var iterate = require('../internals/iterate');
+
+// `Map.prototype.findKey` method
+// https://github.com/tc39/proposal-collection-methods
+$({ target: 'Map', proto: true, real: true, forced: IS_PURE }, {
+ findKey: function findKey(callbackfn /* , thisArg */) {
+ var map = anObject(this);
+ var iterator = getMapIterator(map);
+ var boundFunction = bind(callbackfn, arguments.length > 1 ? arguments[1] : undefined, 3);
+ return iterate(iterator, function (key, value) {
+ if (boundFunction(value, key, map)) return iterate.stop(key);
+ }, undefined, true, true).result;
+ }
+});