1var arrayPush = require('./_arrayPush'),
2    isFlattenable = require('./_isFlattenable');
3
4/**
5 * The base implementation of `_.flatten` with support for restricting flattening.
6 *
7 * @private
8 * @param {Array} array The array to flatten.
9 * @param {number} depth The maximum recursion depth.
10 * @param {boolean} [predicate=isFlattenable] The function invoked per iteration.
11 * @param {boolean} [isStrict] Restrict to values that pass `predicate` checks.
12 * @param {Array} [result=[]] The initial result value.
13 * @returns {Array} Returns the new flattened array.
14 */
15function baseFlatten(array, depth, predicate, isStrict, result) {
16  var index = -1,
17      length = array.length;
18
19  predicate || (predicate = isFlattenable);
20  result || (result = []);
21
22  while (++index < length) {
23    var value = array[index];
24    if (depth > 0 && predicate(value)) {
25      if (depth > 1) {
26        // Recursively flatten arrays (susceptible to call stack limits).
27        baseFlatten(value, depth - 1, predicate, isStrict, result);
28      } else {
29        arrayPush(result, value);
30      }
31    } else if (!isStrict) {
32      result[result.length] = value;
33    }
34  }
35  return result;
36}
37
38module.exports = baseFlatten;
39