'use strict';
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const internals = {};
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module.exports = function (array1, array2, options = {}) {
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if (!array1 ||
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!array2) {
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return (options.first ? null : []);
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}
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const common = [];
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const hash = (Array.isArray(array1) ? new Set(array1) : array1);
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const found = new Set();
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for (const value of array2) {
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if (internals.has(hash, value) &&
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!found.has(value)) {
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if (options.first) {
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return value;
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}
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common.push(value);
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found.add(value);
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}
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}
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return (options.first ? null : common);
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};
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internals.has = function (ref, key) {
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if (typeof ref.has === 'function') {
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return ref.has(key);
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}
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return ref[key] !== undefined;
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};
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