1var Stack = require('./_Stack'),
2    assignMergeValue = require('./_assignMergeValue'),
3    baseFor = require('./_baseFor'),
4    baseMergeDeep = require('./_baseMergeDeep'),
5    isObject = require('./isObject'),
6    keysIn = require('./keysIn'),
7    safeGet = require('./_safeGet');
8
9/**
10 * The base implementation of `_.merge` without support for multiple sources.
11 *
12 * @private
13 * @param {Object} object The destination object.
14 * @param {Object} source The source object.
15 * @param {number} srcIndex The index of `source`.
16 * @param {Function} [customizer] The function to customize merged values.
17 * @param {Object} [stack] Tracks traversed source values and their merged
18 *  counterparts.
19 */
20function baseMerge(object, source, srcIndex, customizer, stack) {
21  if (object === source) {
22    return;
23  }
24  baseFor(source, function(srcValue, key) {
25    stack || (stack = new Stack);
26    if (isObject(srcValue)) {
27      baseMergeDeep(object, source, key, srcIndex, baseMerge, customizer, stack);
28    }
29    else {
30      var newValue = customizer
31        ? customizer(safeGet(object, key), srcValue, (key + ''), object, source, stack)
32        : undefined;
33
34      if (newValue === undefined) {
35        newValue = srcValue;
36      }
37      assignMergeValue(object, key, newValue);
38    }
39  }, keysIn);
40}
41
42module.exports = baseMerge;
43