lodash/internal/baseReduce.js

/**
 * The base implementation of `_.reduce` and `_.reduceRight` without support
 * for callback shorthands or `this` binding, which iterates over `collection`
 * using the provided `eachFunc`.
 *
 * @private
 * @param {Array|Object|string} collection The collection to iterate over.
 * @param {Function} iteratee The function invoked per iteration.
 * @param {*} accumulator The initial value.
 * @param {boolean} initFromCollection Specify using the first or last element
 *  of `collection` as the initial value.
 * @param {Function} eachFunc The function to iterate over `collection`.
 * @returns {*} Returns the accumulated value.
 */
function baseReduce(collection, iteratee, accumulator, initFromCollection, eachFunc) {
  eachFunc(collection, function(value, index, collection) {
    accumulator = initFromCollection
      ? (initFromCollection = false, value)
      : iteratee(accumulator, value, index, collection)
  });
  return accumulator;
}

export default baseReduce;