var baseFlatten = require('./_baseFlatten'),
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baseIteratee = require('./_baseIteratee'),
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baseRest = require('./_baseRest'),
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baseUniq = require('./_baseUniq'),
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isArrayLikeObject = require('./isArrayLikeObject'),
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last = require('./last');
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/**
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* This method is like `_.union` except that it accepts `iteratee` which is
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* invoked for each element of each `arrays` to generate the criterion by
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* which uniqueness is computed. Result values are chosen from the first
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* array in which the value occurs. The iteratee is invoked with one argument:
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* (value).
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*
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* @static
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* @memberOf _
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* @since 4.0.0
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* @category Array
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* @param {...Array} [arrays] The arrays to inspect.
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* @param {Function} [iteratee=_.identity] The iteratee invoked per element.
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* @returns {Array} Returns the new array of combined values.
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* @example
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*
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* _.unionBy([2.1], [1.2, 2.3], Math.floor);
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* // => [2.1, 1.2]
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*
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* // The `_.property` iteratee shorthand.
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* _.unionBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
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* // => [{ 'x': 1 }, { 'x': 2 }]
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*/
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var unionBy = baseRest(function(arrays) {
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var iteratee = last(arrays);
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if (isArrayLikeObject(iteratee)) {
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iteratee = undefined;
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}
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return baseUniq(baseFlatten(arrays, 1, isArrayLikeObject, true), baseIteratee(iteratee, 2));
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});
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module.exports = unionBy;
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