正则表达式匹配连续的-。 或字符串中的.-（连字符和点）

Question

I have a scenario where consecutive -. or .- should not be allowed in a URL.

Eg. https://www.test.-nic or https://www.test-.nic whereas https://www.test.nic--xn/ should be allowed

Can you help me improve this regular expression?

/^(http|https|ftp):\/\/[a-z0-9]+(.[a-z0-9-]+)*.[a-z0-9]{2,5}(:[0-9]{1,5})?(\/.-‌​*)?$/i

Answer 1

You can use negative lookahead:

/^(https?|ftp):\/\/(?=.*?(?:\.-|-\.)[a-z0-9]+(\.[a-z0-9-]+)*\.[a-z0-9]{2,5}(:[0-9]{1,5})?$/i

(?=.*?(?:\\.-|-\\.) is a negative lookahead that will fail the match if ._ or -. are there in the URL.