/**
 * 拓展对象
 */
exports.extend = function extend(target) {
  var sources = Array.prototype.slice.call(arguments, 1)

  for (var i = 0; i < sources.length; i += 1) {
    var source = sources[i]
    for (var key in source) {
      if (source.hasOwnProperty(key)) {
        target[key] = source[key]
      }
    }
  }

  return target
}
