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30 lines
1.0 KiB
30 lines
1.0 KiB
2 years ago
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'use strict';
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var $ = require('../internals/export');
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var call = require('../internals/function-call');
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var uncurryThis = require('../internals/function-uncurry-this');
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var isCallable = require('../internals/is-callable');
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var aCallable = require('../internals/a-callable');
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var iterate = require('../internals/iterate');
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var Map = require('../internals/map-helpers').Map;
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var push = uncurryThis([].push);
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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, forced: true }, {
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groupBy: function groupBy(iterable, keyDerivative) {
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var C = isCallable(this) ? this : Map;
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var newMap = new C();
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aCallable(keyDerivative);
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var has = aCallable(newMap.has);
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var get = aCallable(newMap.get);
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var set = aCallable(newMap.set);
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iterate(iterable, function (element) {
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var derivedKey = keyDerivative(element);
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if (!call(has, newMap, derivedKey)) call(set, newMap, derivedKey, [element]);
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else push(call(get, newMap, derivedKey), element);
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});
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return newMap;
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}
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});
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