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 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                              n r       -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

User · Answer

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

User · Answer

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

User · Answer

for example I faced this in express node js when trying to create route for paths not starting with  internal app get       internal       req  res   gt    and after long trying it just worked when passing it as a RegExp Object using new RegExp   app get new RegExp  quot      internal    quot     req  res   gt    this may help if you are getting this common issue in routing

User · Answer

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

User · 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                          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

User · Answer

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

[javascript] Javascript + Regex = Nothing to repeat error?

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