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Editorial Team
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Asked: 2026-06-13T17:36:09+00:00

I need to know if there is a regular expression for testing for the

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I need to know if there is a regular expression for testing for the presence of numbers in strings that:

  • Matches Lorem 20 Ipsum
  • Matches Lorem 2,5 Ipsum
  • Matches Lorem 20.5 Ipsum
  • Does not match Lorem 2% Ipsum
  • Does not match Lorem 20.5% Ipsum
  • Does not match Lorem 20,5% Ipsum
  • Does not match Lorem 2 percent Ipsum
  • Does not match Lorem 20.5 percent Ipsum
  • Does not match Lorem 20,5 percent Ipsum
  • Matches Lorem 20 Ipsum 2% dolor
  • Matches Lorem 2,5 Ipsum 20.5% dolor
  • Matches Lorem 20.5 Ipsum 20,5% dolor

That is, a regular expression that can tell me if in a string there is one or many numbers, but not as percentage value.

I’ve tried something as /[0-9\.,]+[^%]/, but this not seems to work, I think because digits then not a percentage sign match also the 20 in the string 20%. Additionally, I don’t know how to tell not the entire percent string in addition to the % char.

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1 Answer

  1. Editorial Team

    This will do what you need:

    \b                     -- word boundary
\d+                    -- one or more digits
(?:\.\d+)?             -- optionally followed by a period and one or more digits
\b                     -- word boundary
\s+                    -- one or more spaces
(?!%|percent)          -- NOT followed by a % or the word 'percent'

    –EDIT–

    The meat here is the use of a “negative lookahead” on the final line that causes the match to fail if any of a percent-sign or the literal “percent” occurs after a number and one or more spaces. Other uses of negative lookahead in JavaScript RegExps can be found at Negative lookahead Regular Expression

    –2ND EDIT–
    Congrats to Enrico for solving the most general case but while his solution below is correct, it contains several extraneous operators. Here is the most succinct solution.

    (                         -- start capture
  \d+                     -- one or more digits
  (?:[\.,]\d+)?           -- optional period or comma followed by one or more digits
  \b                      -- word boundary
  (?!                     -- start negative lookahead
    (?:[\.,]\d+)          -- must not be followed by period or comma plus digits
  |                       --    or
    (?:                   -- start option group
      \s?%                -- optional space plus percent sign
    |                     --   or
      \spercent           -- required space and literal 'percent'
    )                     -- end option group
  )                       -- end negative lookahead
)                         -- end capture group
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