Studying all day long)
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'use strict';
var $ = require('../internals/export');
var getBuiltIn = require('../internals/get-built-in');
var bind = require('../internals/function-bind-context');
var call = require('../internals/function-call');
var aCallable = require('../internals/a-callable');
var anObject = require('../internals/an-object');
var speciesConstructor = require('../internals/species-constructor');
var getMapIterator = require('../internals/get-map-iterator');
var iterate = require('../internals/iterate');
// `Map.prototype.mapKeys` method
// https://github.com/tc39/proposal-collection-methods
$({ target: 'Map', proto: true, real: true, forced: true }, {
mapKeys: function mapKeys(callbackfn /* , thisArg */) {
var map = anObject(this);
var iterator = getMapIterator(map);
var boundFunction = bind(callbackfn, arguments.length > 1 ? arguments[1] : undefined);
var newMap = new (speciesConstructor(map, getBuiltIn('Map')))();
var setter = aCallable(newMap.set);
iterate(iterator, function (key, value) {
call(setter, newMap, boundFunction(value, key, map), value);
}, { AS_ENTRIES: true, IS_ITERATOR: true });
return newMap;
}
});