CODEWITHSUNDEEP
javascriptregexrange
zana10
zana10

Reputation: 113

Regular expression range with decimal 0.1 to 1

I' am using following regex:

/^(?:1|0?\.\d)$/

I need range between 0.1 and 1 with each number before and after dot. For example:

0.1 valid
1 valid
0.111 not valid
011.2 not valid

Valid numbers are [0.1-0.9] and 1

Upvotes: 0

Views: 1446

Answers (3)

Ryszard Czech
Ryszard Czech

Reputation: 18611

Use

/^(?:1|0?\.[1-9])$/

See proof

Explanation

--------------------------------------------------------------------------------
  ^                        the beginning of the string
--------------------------------------------------------------------------------
  (?:                      group, but do not capture:
--------------------------------------------------------------------------------
    1                        '1'
--------------------------------------------------------------------------------

   |                        OR
--------------------------------------------------------------------------------
    0?                       '0' (optional (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    \.                       '.'
--------------------------------------------------------------------------------
    [1-9]                    any character of: '1' to '9'
--------------------------------------------------------------------------------
  )                        end of grouping
--------------------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string

Upvotes: 1

Steven
Steven

Reputation: 6148

Bob's answer is along the right lines, however, it can do with some tweaking...

  • So that it doesn't match 1. | .1
  • So that returned captures don't include \n
  • So that the returned matches are a single dimension array

RegEx

(?<=^|[^[0-9]\.])(0\.[1-9]|1)(?=$|[^[0-9]\.])
(?<=                                            : Start of positive look behind
    ^                                           : Matches start of string
     |                                          : OR operator
      [^0-9\.]                                : Matches anything but 0-9 or literal "."
                )                               : End of look behind group
                 (                              : Start of capture group
                  0\.[1-9]                      : Matches 0.1 -> 0.9
                          |                     : OR operator
                           1                    : Matches 1 on it's own
                            )                   : End of capture group
                             (?=                : Start of positive look ahead
                                $               : Matches end of string
                                 |              : OR operator
                                  [^0-9\.]    : Matches anything BUT 0-9 or literal "."
                                            )   : End of look ahead

Alternative style

The range 0-9 can also be adjusted:

[0-9] == \d

(?<=^|[^\d\.])(0\.[1-9]|1)(?=$|[^\d\.])

Flags

You will also need to implement a couple of RegEx flags:

g    : Global
m    : Multiline mode

JS Example

var data = `
0.1    : Match
1      : Match
0.111  : No-match
011.2  : No-match
1.2    : No-match
0.2    : Match
0      : No-match
0.1    : Match
.1     : No-match
1.0    : Match
`;

var re = /(?<=^|[^\d\.])(0\.[1-9]|1)(?=$|[^\d\.])/gm;

console.log(data.match(re));  // Output: ["0.1", "1", "0.2", "0.1"]

Upvotes: 0

Bob Jarvis - Слава Україні
Bob Jarvis - Слава Україні

Reputation: 50017

The following works for the given test data:

(^|[^0-9])(0\.[1-9]|1\.0|1)($|[^0-9])

regex101 example here

Upvotes: 1

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