Updated the check of isFunction method (#4555)

isFunction.js

@@ -1,5 +1,3 @@
-import getTag from './.internal/getTag.js'
-import isObject from './isObject.js'
 
 /**
  * Checks if `value` is classified as a `Function` object.
@@ -10,21 +8,26 @@ import isObject from './isObject.js'
  * @returns {boolean} Returns `true` if `value` is a function, else `false`.
  * @example
  *
- * isFunction(_)
+ * isFunction(class Any{})
  * // => true
  *
+ * isFunction(() => {})
+ * // => true
+ * 
+ * isFunction(async () => {})
+ * // => true
+ * 
+ * isFunction(function * Any() {})
+ * // => true
+ * 
+ * isFunction(Math.round)
+ * // => true
+ * 
  * isFunction(/abc/)
  * // => false
  */
 function isFunction(value) {
-  if (!isObject(value)) {
+  return typeof value === 'function'
-    return false
-  }
-  // The use of `Object#toString` avoids issues with the `typeof` operator
-  // in Safari 9 which returns 'object' for typed arrays and other constructors.
-  const tag = getTag(value)
-  return tag == '[object Function]' || tag == '[object AsyncFunction]' ||
-    tag == '[object GeneratorFunction]' || tag == '[object Proxy]'
 }
 
 export default isFunction