1'use strict';
2// https://tc39.github.io/proposal-flatMap/#sec-FlattenIntoArray
3var isArray = require('./_is-array');
4var isObject = require('./_is-object');
5var toLength = require('./_to-length');
6var ctx = require('./_ctx');
7var IS_CONCAT_SPREADABLE = require('./_wks')('isConcatSpreadable');
8
9function flattenIntoArray(target, original, source, sourceLen, start, depth, mapper, thisArg) {
10  var targetIndex = start;
11  var sourceIndex = 0;
12  var mapFn = mapper ? ctx(mapper, thisArg, 3) : false;
13  var element, spreadable;
14
15  while (sourceIndex < sourceLen) {
16    if (sourceIndex in source) {
17      element = mapFn ? mapFn(source[sourceIndex], sourceIndex, original) : source[sourceIndex];
18
19      spreadable = false;
20      if (isObject(element)) {
21        spreadable = element[IS_CONCAT_SPREADABLE];
22        spreadable = spreadable !== undefined ? !!spreadable : isArray(element);
23      }
24
25      if (spreadable && depth > 0) {
26        targetIndex = flattenIntoArray(target, original, element, toLength(element.length), targetIndex, depth - 1) - 1;
27      } else {
28        if (targetIndex >= 0x1fffffffffffff) throw TypeError();
29        target[targetIndex] = element;
30      }
31
32      targetIndex++;
33    }
34    sourceIndex++;
35  }
36  return targetIndex;
37}
38
39module.exports = flattenIntoArray;
40