var eq = require('./eq');

/** Used for built-in method references. */ var objectProto = Object.prototype;

/** Used to check objects for own properties. */ var hasOwnProperty = objectProto.hasOwnProperty;

/**

* Used by `_.defaults` to customize its `_.assignIn` use to assign properties
* of source objects to the destination object for all destination properties
* that resolve to `undefined`.
*
* @private
* @param {*} objValue The destination value.
* @param {*} srcValue The source value.
* @param {string} key The key of the property to assign.
* @param {Object} object The parent object of `objValue`.
* @returns {*} Returns the value to assign.
*/

function customDefaultsAssignIn(objValue, srcValue, key, object) {

if (objValue === undefined ||
    (eq(objValue, objectProto[key]) && !hasOwnProperty.call(object, key))) {
  return srcValue;
}
return objValue;

}

module.exports = customDefaultsAssignIn;