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- 'use strict';
- var $ = require('../internals/export');
- var uncurryThis = require('../internals/function-uncurry-this');
- var aCallable = require('../internals/a-callable');
- var requireObjectCoercible = require('../internals/require-object-coercible');
- var iterate = require('../internals/iterate');
- var MapHelpers = require('../internals/map-helpers');
- var IS_PURE = require('../internals/is-pure');
- var Map = MapHelpers.Map;
- var has = MapHelpers.has;
- var get = MapHelpers.get;
- var set = MapHelpers.set;
- var push = uncurryThis([].push);
- // `Map.groupBy` method
- // https://github.com/tc39/proposal-array-grouping
- $({ target: 'Map', stat: true, forced: IS_PURE }, {
- groupBy: function groupBy(items, callbackfn) {
- requireObjectCoercible(items);
- aCallable(callbackfn);
- var map = new Map();
- var k = 0;
- iterate(items, function (value) {
- var key = callbackfn(value, k++);
- if (!has(map, key)) set(map, key, [value]);
- else push(get(map, key), value);
- });
- return map;
- }
- });
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