Fix typos

snippets/formatSeconds.md

@@ -12,7 +12,7 @@ Returns the ISO format of the given number of seconds.
 - Divide `s` with the appropriate values to obtain the appropriate values for `hour`, `minute` and `second`.
 - Store the `sign` in a variable to prepend it to the result.
 - Use `Array.prototype.map()` in combination with `Math.floor()` and `String.prototype.padStart()` to stringify and format each segment.
-- Use `String.prototype.join()` to combine the values into a string.
+- Use `Array.prototype.join()` to combine the values into a string.
 
 ```js
 const formatSeconds = s => {