internal/baseIntersection.js

import SetCache from './SetCache';
import arrayIncludes from './arrayIncludes';
import arrayIncludesWith from './arrayIncludesWith';
import arrayMap from './arrayMap';
import baseUnary from './baseUnary';
import cacheHas from './cacheHas';

/**
 * The base implementation of methods like `_.intersection`, without support
 * for iteratee shorthands, that accepts an array of arrays to inspect.
 *
 * @private
 * @param {Array} arrays The arrays to inspect.
 * @param {Function} [iteratee] The iteratee invoked per element.
 * @param {Function} [comparator] The comparator invoked per element.
 * @returns {Array} Returns the new array of shared values.
 */
function baseIntersection(arrays, iteratee, comparator) {
  var includes = comparator ? arrayIncludesWith : arrayIncludes,
      othLength = arrays.length,
      othIndex = othLength,
      caches = Array(othLength),
      result = [];

  while (othIndex--) {
    var array = arrays[othIndex];
    if (othIndex && iteratee) {
      array = arrayMap(array, baseUnary(iteratee));
    }
    caches[othIndex] = !comparator && (iteratee || array.length >= 120)
      ? new SetCache(othIndex && array)
      : undefined;
  }
  array = arrays[0];

  var index = -1,
      length = array.length,
      seen = caches[0];

  outer:
  while (++index < length) {
    var value = array[index],
        computed = iteratee ? iteratee(value) : value;

    if (!(seen ? cacheHas(seen, computed) : includes(result, computed, comparator))) {
      var othIndex = othLength;
      while (--othIndex) {
        var cache = caches[othIndex];
        if (!(cache ? cacheHas(cache, computed) : includes(arrays[othIndex], computed, comparator))) {
          continue outer;
        }
      }
      if (seen) {
        seen.push(computed);
      }
      result.push(value);
    }
  }
  return result;
}

export default baseIntersection;