JS regex string validation for slug

Question

I have an app, that allowing the end user to enter his desired slug. What I am looking for is a regex that check if the slug is valid.

In general, as valid a mean a string that start and ends with a latin leter, divided by dashes but not more than one dashes.

More specific, the following is correct:

one-two-three

The following are not:

one---two-thee-
-one-two-three
one-two-three-

So with the following regex I am somewhow ok, but how can I check if in the middle of the string there are no more than two dashes ?

^[a-z][a-z][a-z]$

Is there a better way to write this regex, in order to meet my validation creteria ?

Answer 1

http://regexpal.com/ can be a great webpage for checking your regexes as you write them. A handy tool :).

Having a look at yours, should it accept capital letters/numbers? If so maybe this will help :

/^[A-Za-z0-9]+(?:-[A-Za-z0-9]+)*$/

This will only match sequences of one or more sequences of alphanumeric characters separated by a single -. If you do not want to allow single words (e.g. just hello), replace the * multiplier with + to allow only one or more repetitions of the last group.

Here's a link to a live sample from the same thread to demonstrate.

Changing around the A-Za-z0-9 inside the squares will allow you to only accept capitals,non-capitals or numbers as is appropriate to you.

Good luck and let me know if you have any more questions ! :)

Answer 2

My personal favourite :

^[a-z](-?[a-z])*$

Begin with a lowercase letter; then more lower or maybe a hyphen, but not without another lower right after it.

Answer 3

^[a-z][a-z\-]*[a-z]$

actually this should be your regex and your validation should be tested in two phases.

The first one by this regex, which will be a basic test, the second one can be done by splitting on hiphens and checking again the same regex on the splitted strings.