Question :
For me it is always better to exemplify regex cases. See:
- Word1 – Valid
- Word2 – Valid
- Word1 Word2 – Valid
- Word2 Word1 – Valid
- Word1 Word1 – Invalid
- Word2 Word2 – Invalid
But let’s say 5 or 6 words, it is very costly to write ALL the possibilities
Answer :
It is difficult with regex to know if there is a sequence without repetitions, but it is easy to know if there is a repetition of words. Using a capturing group you can check if a given word returns to the string.
You can use a regex like this:
b(w+)s[sw]*
It looks for a word b(w+) followed by a space s (to be sure another word will come), and then searches the string for a repeat of what was previously caught with .
regex example: link
jsFiddle: link