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22 lines
755 B
22 lines
755 B
'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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