var arrayReduce = require('../internal/arrayReduce'),
    baseEach = require('../internal/baseEach'),
    createReduce = require('../internal/createReduce');

/**
 * Reduces `collection` to a value which is the accumulated result of running
 * each element in `collection` through `iteratee`, where each successive
 * invocation is supplied the return value of the previous. If `accumulator`
 * is not provided the first element of `collection` is used as the initial
 * value. The `iteratee` is bound to `thisArg` and invoked with four arguments:
 * (accumulator, value, index|key, collection).
 *
 * Many lodash methods are guarded to work as iteratees for methods like
 * `_.reduce`, `_.reduceRight`, and `_.transform`.
 *
 * The guarded methods are:
 * `assign`, `defaults`, `defaultsDeep`, `includes`, `merge`, `sortByAll`,
 * and `sortByOrder`
 *
 * @static
 * @memberOf _
 * @alias foldl, inject
 * @category Collection
 * @param {Array|Object|string} collection The collection to iterate over.
 * @param {Function} [iteratee=_.identity] The function invoked per iteration.
 * @param {*} [accumulator] The initial value.
 * @param {*} [thisArg] The `this` binding of `iteratee`.
 * @returns {*} Returns the accumulated value.
 * @example
 *
 * _.reduce([1, 2], function(total, n) {
 *   return total + n;
 * });
 * // => 3
 *
 * _.reduce({ 'a': 1, 'b': 2 }, function(result, n, key) {
 *   result[key] = n * 3;
 *   return result;
 * }, {});
 * // => { 'a': 3, 'b': 6 } (iteration order is not guaranteed)
 */
var reduce = createReduce(arrayReduce, baseEach);

module.exports = reduce;