'use strict';
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var $ = require('../internals/export');
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var getBuiltIn = require('../internals/get-built-in');
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var uncurryThis = require('../internals/function-uncurry-this');
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var aCallable = require('../internals/a-callable');
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var requireObjectCoercible = require('../internals/require-object-coercible');
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var toPropertyKey = require('../internals/to-property-key');
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var iterate = require('../internals/iterate');
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var create = getBuiltIn('Object', 'create');
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var push = uncurryThis([].push);
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// `Object.groupBy` method
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// https://github.com/tc39/proposal-array-grouping
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$({ target: 'Object', stat: true }, {
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groupBy: function groupBy(items, callbackfn) {
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requireObjectCoercible(items);
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aCallable(callbackfn);
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var obj = create(null);
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var k = 0;
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iterate(items, function (value) {
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var key = toPropertyKey(callbackfn(value, k++));
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// in some IE versions, `hasOwnProperty` returns incorrect result on integer keys
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// but since it's a `null` prototype object, we can safely use `in`
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if (key in obj) push(obj[key], value);
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else obj[key] = [value];
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});
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return obj;
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}
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});
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