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