Reverse the word order, keep the spaces

Write a function reverseWordOrder(sentence) that returns a new string with the words in reverse order. The spaces between the words stay where they are: 'This is sample text' becomes 'text sample is This'.

• A word is a run of characters that are not spaces. Punctuation is part of the word.
• Words are separated only by spaces (no tabs, no line breaks). A gap can be one space or more.
• Every gap of whitespace keeps its length and its place, also at the start and at the end of the string. Only the words move: ' Hello world ' becomes ' world Hello '.
• The words themselves are not reversed.
• A string without words (empty or only spaces) is returned unchanged.

If you split on one space and join back with one space, the gaps move together with the words. A loop or a regular expression that finds the words and the gaps works better.