Regex to match any set of numbers except the 10 digit numbers starting with 7

Question

I want to capture all numbers(any no.of digits) except the 10 digit numbers starting with 7.

71234567890 - should match
7123456789 - should not match
1234567890- should match

Answer 1

Use the pattern

/7\d{9}|(\d+)/
 ^^^^^^           MATCH 10-DIGIT NUMBER STARTING WITH SEVEN, DO NOT CAPTURE
       ^          --OR--
        ^^^^^     MATCH OTHER SEQUENCES OF DIGITS AND DO CAPTURE

This will match the 10-digit number starting with 7 but not capture it; otherwise, it will match the sequence of digits and capture it.

Now

'7123456789'.match(regexp)
["7123456789", undefined]

'1234567890'.match(regexp)
["1234567890", "1234567890"]

In other words, the captured string will be found in the second element of the array returned by match .

If you want to anchor this to the beginning and end of the string, then

/^7\d{9}$|(^\d+$)/

You could also do this with a negative look-ahead, as suggested in the comments, but it's not needed here and could be a bit of a stretch for beginning regexpers.

Answer 2

(?:(?:^|\D)(7\d{1,8}|7\d{10,})(?:\D|$))

看演示

Answer 3

In order to get any number of digits except a string of 10 digits starting with '7'
you'd have to special case the '7'. There is really no way around it.

The fastest way is a pure regex solution, since the engine stays inside
running c++ engine code and does not interact with the host language.

There are two ways, either anchored or mid-string.

Anchored: ^(?:7(?!\\d{9}$)|[012345689])\\d*$
( number string is the overall match, ie in capture group 0 )

 ^                    # Beginning of string
 (?:                  # Cluster, get first digit
      7                    # '7'
      (?! \d{9} $)         #  not followed by nine more digits
   |                     # or 
      [012345689]          # Any digit except '7' (i.e. [^\D7])
 )                    # End cluster
 \d*                  # Get optional remaining digits
 $   

Mid-string: (?:^|\\D)((?:7(?!\\d{9}(?:\\D|$))|[012345689])\\d*)
( number string is in capture group 1 )

 (?: ^ | \D )         # Beginning of string or not a digit
 (                    # (1 start), The number
      (?:                  # Cluster, get first digit
           7                    # '7'
           (?!                  # Assertion, not followed by nine more digits
                \d{9} 
                (?: \D | $ )         #  (forces no more/less than nine) digits
           )
        |                     # or 
           [012345689]          # Any digit except '7' (i.e. [^\D7])
      )                    # End cluster
      \d*                  # Get optional remaining digits
 )                    # (1 end)