I have the following regex: /\.([s]?[ac]ss)$/. The problem is, it matches .scss, .sass, .css, .ass. How would I make it not match .ass?

CodePudding user response：

Also this will match .scss, .sass and .css only, it is very readable and self-explanatory

/\.(sc|sa|c)ss$/

CodePudding user response：

You can use

\.(?!a)(s?[ac]ss)$

See the

CodePudding user response：

In your pattern \.([s]?[ac]ss)$ you match .ass because the leading s optional and the character class [ac] can match both characters.

Instead you could use lookarounds assertions, or use an alternation | to allow only certain alternatives.

Some other variations could be:

\.(s?c|sa)ss$

• \.Match a .
• ( Capture group 1
  • s?c|sa Match an optional s then match c or match sa
• ) Close group 1
• ss$ Match ss at the end of the string

Regex demo

\.(s[ac]|c)ss$

A variation on the previous pattern, now matching sa or sc or c

Regex demo

If in your environment the lookbehind assertion is supported:

\.s?[ac]ss$(?<!\.ass)

• \.s? Match a . and optional s
• [ac] Match either a or c
• ss$ Match ss at the end of the string
• (?<!\.ass) Negative lookbehind, assert not .ass to the left

Regex demo

Note that if you want a match only, you can also use a non capture group (?:...) instead.