internal/baseSet.js

import assignValue from './assignValue';
import baseToPath from './baseToPath';
import isIndex from './isIndex';
import isKey from './isKey';
import isObject from '../isObject';

/**
 * The base implementation of `_.set`.
 *
 * @private
 * @param {Object} object The object to query.
 * @param {Array|string} path The path of the property to set.
 * @param {*} value The value to set.
 * @param {Function} [customizer] The function to customize path creation.
 * @returns {Object} Returns `object`.
 */
function baseSet(object, path, value, customizer) {
  path = isKey(path, object) ? [path + ''] : baseToPath(path);

  var index = -1,
      length = path.length,
      lastIndex = length - 1,
      nested = object;

  while (nested != null && ++index < length) {
    var key = path[index];
    if (isObject(nested)) {
      var newValue = value;
      if (index != lastIndex) {
        var objValue = nested[key];
        newValue = customizer ? customizer(objValue, key, nested) : undefined;
        if (newValue === undefined) {
          newValue = objValue == null ? (isIndex(path[index + 1]) ? [] : {}) : objValue;
        }
      }
      assignValue(nested, key, newValue);
    }
    nested = nested[key];
  }
  return object;
}

export default baseSet;