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What does the Nothing to repeat error mean when using a regex in javascript?

rated 0 times [ 72] [ 4] / answers: 1 / hits: 174849 / 13 Years ago, thu, june 9, 2011, 12:00:00

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 here.

I'm trying to see if the user's input has illegal characters in it by using the .search function as so:

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

    ...

}

However, when I try to execute the function this line is contained it, it throws the following error for that specific line:

Uncaught SyntaxError: Invalid regular expression: /[[]?*+|{}()@.



]/: Nothing to repeat

I can't for the life of me see what's wrong with my code. Can anyone point me in the right direction?

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jesse

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2 Years ago

answered 13 Years ago frederickmohamedw · Accepted Answer

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:

[\[\]?*+|{}\\()@.nr]

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.