Update snippet descriptions

snippets/mapString.md

@@ -3,7 +3,7 @@ title: mapString
 tags: string,intermediate
 ---
 
-Creates a new string with the results of calling a provided function on every character in the calling string.
+Creates a new string with the results of calling a provided function on every character in the given string.
 
 - Use `String.prototype.split('')` and `Array.prototype.map()` to call the provided function, `fn`, for each character in `str`.
 - Use `Array.prototype.join('')` to recombine the array of characters into a string.