33 lines
1.0 KiB
JavaScript
33 lines
1.0 KiB
JavaScript
'use strict';
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var toLength = require('../internals/to-length');
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var toObject = require('../internals/to-object');
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var getBuiltIn = require('../internals/get-built-in');
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var arraySpeciesCreate = require('../internals/array-species-create');
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var push = [].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 = toLength(that.length);
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var result = arraySpeciesCreate(that, 0);
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var Map = getBuiltIn('Map');
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var map = new Map();
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var resolverFunction, index, item, key;
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if (typeof resolver == 'function') resolverFunction = resolver;
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else if (resolver == null) resolverFunction = function (value) {
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return value;
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};
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else throw new TypeError('Incorrect resolver!');
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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 (!map.has(key)) map.set(key, item);
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}
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map.forEach(function (value) {
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push.call(result, value);
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});
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return result;
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};
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