How can I match on, but exclude a regex pattern?

Question

I have this URL:

http://example.com/createSend/step4_1.aspx?cID=876XYZ964D293CF&snap=true&jlkj=kjhkjh&

And this regex pattern:

cID=[^&]* 

Which produces this result:

cID=87B6XYZ964D293CF 

How do I REMOVE the "cID="?

Thanks

Answer 1

You can either use lookbehind (not in Javascript):

(?<=cID=)[^&]* 

Or you can use grouping and grab the first group:

cID=([^&]*) 

Answer 2

Generally speaking, to accomplish something like this, you have at least 3 options:

• Use lookarounds, so you can match precisely what you want to capture
  • No lookbehind in Javascript, unfortunately
• Use capturing group to capture specific strings
  • Near universally supported in all flavors
• If all else fails, you can always just take a substring of the match
  • Works well if the length of the prefix/suffix to chop is a known constant

References

• w3schools - jsref - substring
• regular-expressions.info/Capturing groups and Lookarounds
  • Flavor comparison

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Examples

Given this test string:

i have 35 dogs, 16 cats and 10 elephants 

These are the matches of some regex patterns:

• \d+ cats -> 16 cats (see on rubular.com)
• \d+(?= cats) -> 16 (see on rubular.com)
• (\d+) cats -> 16 cats (see on rubular.com)
  • Group 1 captures 16

You can also do multiple captures, for example:

• (\d+) (cats|dogs) yields 2 match results (see on rubular.com)
  • Result 1: 35 dogs
    • Group 1 captures 35
    • Group 2 captures dogs
  • Result 2: 16 cats
    • Group 1 captures 16
    • Group 2 captures cats