'use strict';
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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 lengthOfArrayLike = require('../internals/length-of-array-like');
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var toObject = require('../internals/to-object');
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var arraySpeciesCreate = require('../internals/array-species-create');
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var Map = getBuiltIn('Map');
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var MapPrototype = Map.prototype;
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var mapForEach = uncurryThis(MapPrototype.forEach);
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var mapHas = uncurryThis(MapPrototype.has);
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var mapSet = uncurryThis(MapPrototype.set);
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var push = uncurryThis([].push);
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// `Array.prototype.uniqueBy` method
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// https://github.com/tc39/proposal-array-unique
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module.exports = function uniqueBy(resolver) {
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var that = toObject(this);
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var length = lengthOfArrayLike(that);
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var result = arraySpeciesCreate(that, 0);
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var map = new Map();
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var resolverFunction = resolver != null ? aCallable(resolver) : function (value) {
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return value;
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};
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var index, item, key;
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for (index = 0; index < length; index++) {
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item = that[index];
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key = resolverFunction(item);
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if (!mapHas(map, key)) mapSet(map, key, item);
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}
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mapForEach(map, function (value) {
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push(result, value);
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});
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return result;
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};
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