function keysIn(object) {
  if (object == null) {
    return [];
  }
  if (!isObject(object)) {
    object = Object(object);
  }
  var length = object.length;

  length = (length && isLength(length) &&
    (isArray(object) || isArguments(object) || isString(object)) && length) || 0;

  var Ctor = object.constructor,
      index = -1,
      proto = (isFunction(Ctor) && Ctor.prototype) || objectProto,
      isProto = proto === object,
      result = Array(length),
      skipIndexes = length > 0,
      skipErrorProps = support.enumErrorProps && (object === errorProto || object instanceof Error),
      skipProto = support.enumPrototypes && isFunction(object);

  while (++index < length) {
    result[index] = (index + '');
  }
  // lodash skips the `constructor` property when it infers it's iterating
  // over a `prototype` object because IE < 9 can't set the `[[Enumerable]]`
  // attribute of an existing property and the `constructor` property of a
  // prototype defaults to non-enumerable.
  for (var key in object) {
    if (!(skipProto && key == 'prototype') &&
        !(skipErrorProps && (key == 'message' || key == 'name')) &&
        !(skipIndexes && isIndex(key, length)) &&
        !(key == 'constructor' && (isProto || !hasOwnProperty.call(object, key)))) {
      result.push(key);
    }
  }
  if (support.nonEnumShadows && object !== objectProto) {
    var tag = object === stringProto ? stringTag : (object === errorProto ? errorTag : objToString.call(object)),
        nonEnums = nonEnumProps[tag] || nonEnumProps[objectTag];

    if (tag == objectTag) {
      proto = objectProto;
    }
    length = shadowProps.length;
    while (length--) {
      key = shadowProps[length];
      var nonEnum = nonEnums[key];
      if (!(isProto && nonEnum) &&
          (nonEnum ? hasOwnProperty.call(object, key) : object[key] !== proto[key])) {
        result.push(key);
      }
    }
  }
  return result;
}
Creates an array of the own and inherited enumerable property names of `object`.

**Note:** Non-object values are coerced to objects.

@static
@memberOf _
@category Object
@param {Object} object The object to query.
@returns {Array} Returns the array of property names.
@example

function Foo() {
  this.a = 1;
  this.b = 2;
}

Foo.prototype.c = 3;

_.keysIn(new Foo);
// => ['a', 'b', 'c'] (iteration order is not guaranteed)