What does "?-mix:" mean in regex

Question

What does "?-mix:" mean in regex, also is this valid in javascript/jQuery? If it's not valid, what is an appropriate substitute.

Update: This is the full regex /(?-mix:^[^,;]+$)/

Its used in javascript in chrome, and I'm getting the following error:

Uncaught SyntaxError: Invalid regular expression: /(?-mix:^[^,;]+$)/: Invalid group

Note: I found this helpful: How to translate ruby regex to javascript? - (?i-mx:..) and Rails 3.0.3

Answer 1

Assuming perl context, (?-mix) this would

• -m disable multiline matching
• -i disable case insensitive matching
• -x disable extended regex whitespace

See here: http://www.regular-expressions.info/modifiers.html

Not all regex flavors support this. JavaScript and Python apply all mode modifiers to the entire regular expression. They don't support the (?-ismx) syntax, since turning off an option is pointless when mode modifiers apply to the whole regular expressions. All options are off by default.

Answer 2

Since you've now made it clear that the context here is javascript, I don't think javascript supports that flag syntax so it's complaining about ^ being found in the middle of a regex. Since you can never find the start of a match in the middle of a match, this makes an invalid regex.

In javascript, you specify flags outside the regex itself such as:

var re = /^[^,;]+$/mi;

or as an argument like this:

var re = new RegExp("^[^,;]+$", "mi");

The x flag is not supported in javascript and this particular regex does not need the i flag.

What this particular regex is trying to do is to tell you whether the string you are matching it against contains all characters other than , and ; and is not empty.