Update isUpperCase.md

snippets/isUpperCase.md

@@ -1,16 +1,16 @@
 ### isUpperCase
 
-Checks if the provided argument contains anything else than the uppercase alphabets. If the second argument is provided to be true than numbers and other symbols are considered uppercase too.
+Checks if a string is upper case.
+
+Convert the given string to upper case, using `String.toUpperCase()` and compare it to the original.
+
+
 ``` js
-const isUpperCase = (val,symbol = false) => {
-  if (symbol) return val === val.toUpperCase()
-  else return!(/[^A-Z]/g.test(val))
-}
+const isUpperCase = str => str === str.toUpperCase();
 ```
+
 ``` js
-isUpperCase('ABC'); //true
-isUpperCase('ABC123@$'); //false
-isUpperCase('ABC123@$',true); //true
-isUpperCase('ABC123@$abcd',true); //false
-isUpperCase('ABC123@$abcd'); //false
+isUpperCase('ABC'); // true
+isLowerCase('A3@$'); // true
+isLowerCase('aB4'); // false
 ```