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'use strict';
var $ = require('../internals/export');
var iterate = require('../internals/iterate');
var aFunction = require('../internals/a-function');
// `Map.groupBy` method
// https://github.com/tc39/proposal-collection-methods
$({ target: 'Map', stat: true }, {
groupBy: function groupBy(iterable, keyDerivative) {
var newMap = new this();
aFunction(keyDerivative);
var has = aFunction(newMap.has);
var get = aFunction(newMap.get);
var set = aFunction(newMap.set);
iterate(iterable, function (element) {
var derivedKey = keyDerivative(element);
if (!has.call(newMap, derivedKey)) set.call(newMap, derivedKey, [element]);
else get.call(newMap, derivedKey).push(element);
});
return newMap;
}
});
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