Javascript + Regex = Nothing to repeat error?

Question

I\'m new to Regex and I\'m trying to work it into one of my new projects to see if I can learn it and add it to my repitoire of skills. However, I\'m hitting a roadblock her

Answer 1

Well, in my case I had to test a Phone Number with the help of regex, and I was getting the same error,

Invalid regular expression: /+923[0-9]{2}-(?!1234567)(?!1111111)(?!7654321)[0-9]{7}/: Nothing to repeat'

So, what was the error in my case was that + operator after the / in the start of the regex. So enclosing the + operator with square brackets [+], and again sending the request, worked like a charm.

Following will work:

/[+]923[0-9]{2}-(?!1234567)(?!1111111)(?!7654321)[0-9]{7}/

This answer may be helpful for those, who got the same type of error, but their chances of getting the error from this point of view, as mine! Cheers :)

Answer 2

Building off of @Bohemian, I think the easiest approach would be to just use a regex literal, e.g.:

if (name.search(/[\[\]?*+|{}\\()@.\n\r]/) != -1) {
    // ... stuff ...
}

Regex literals are nice because you don't have to escape the escape character, and some IDE's will highlight invalid regex (very helpful for me as I constantly screw them up).

Answer 3

You need to double the backslashes used to escape the regular expression special characters. However, as @Bohemian points out, most of those backslashes aren't needed. Unfortunately, his answer suffers from the same problem as yours. What you actually want is:

The backslash is being interpreted by the code that reads the string, rather than passed to the regular expression parser. You want:

"[\\[\\]?*+|{}\\\\()@.\n\r]"

Note the quadrupled backslash. That is definitely needed. The string passed to the regular expression compiler is then identical to @Bohemian's string, and works correctly.

Answer 4

Firstly, in a character class [...] most characters don't need escaping - they are just literals.

So, your regex should be:

"[\[\]?*+|{}\\()@.\n\r]"

This compiles for me.

Answer 5

For Google travelers: this stupidly unhelpful error message is also presented when you make a type and double up the + regex operator:

Okay:

\w+

Not okay:

\w++