Simplify has and hasIn.

hasIn.js

@@ -1,15 +1,12 @@
-import baseHasIn from './.internal/baseHasIn.js'
-import hasPath from './.internal/hasPath.js'
-
 /**
  * Checks if `path` is a direct or inherited property of `object`.
  *
  * @since 4.0.0
  * @category Object
  * @param {Object} object The object to query.
- * @param {Array|string} path The path to check.
- * @returns {boolean} Returns `true` if `path` exists, else `false`.
- * @see has, get, set, unset
+ * @param {string} key The key to check.
+ * @returns {boolean} Returns `true` if `key` exists, else `false`.
+ * @see has, hasPath, hasPathIn
  * @example
  *
  * const object = create({ 'a': create({ 'b': 2 }) })
@@ -17,17 +14,11 @@ import hasPath from './.internal/hasPath.js'
  * hasIn(object, 'a')
  * // => true
  *
- * hasIn(object, 'a.b')
- * // => true
- *
- * hasIn(object, ['a', 'b'])
- * // => true
- *
  * hasIn(object, 'b')
  * // => false
  */
-function hasIn(object, path) {
-  return object != null && hasPath(object, path, baseHasIn)
+function hasIn(object, key) {
+  return object != null && key in Object(object)
 }
 
 export default hasIn