Regex with range negative value to positive

Hi I need to create regex that will match numbers in range -1 to 1, chat got problem with that and also i didn't find many answers.

Now I'm stuck because my regex match also -1.5 and 1.5 value but it shouldn't, my current regex is: ^-?1(\.0+)?|^-?0(\.[0]+)?$

Try this: ^-?1(\.0+)?|^-?0(\.[0-9]+)?$

Explanation:

• ^ asserts the start of the string.

• -? matches an optional minus sign.
  1(\.0+)? matches the number 1 followed by an optional decimal point and one or more zeros.

• | is the alternation operator, allowing matching either the previous pattern or the next pattern.

• ^-?0(\.[0-9]+)?$ matches the number 0 or a decimal number between -1 and 1.

Examples of matching numbers using this regex:

-1

-0.5

0

0.5

1

Examples of non-matching numbers:

-1.5

1.5

-2

2

The first alternative in your pattern is missing the anchor $

To match all the values in between, you can match either 1 followed by . and 1+ zeroes, or match optional zeroes followed by . and 1+ digits:

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

Explanation

• ^ Start of string
• -? Match optional -
• (?: Non capture group for the alternatives
  • 1(?:\.0+)? Match 1 with an optional part matching . and 1+ zeroes
  • | Or
  • 0+(?:\.\d+)? Match 1 with an optional part matching . and 1+ digits
• ) Close the non capture group
• $ End of string

Regex demo.

If the numbers are properly formatted decimals, all you need is
^-?(0|1|0\.\d+)$

However, if they are not...
Ignoring ^$ bounds and optional -? which are always the same, you need:

• 1(\.0*)? - to parse 1, 1., 1.0
• 0?\.\d+ - to parse 0.123, .123
• 0\.\d* - ro parse 0, 0., 0.123
• \d+(\.\d*)?[eE]-\d+ - to parse 1e-12, 1E-12, 1.e-12, 1.23e-12

(all are valid numbers at least in Javascript)

resulting in ^-?(1(\.0*)?|0?\.\d+|0\.\d*|\d+(\.\d*)?[eE]-\d+)$

(and it's still missing 0.123e1, 12.3e-1 and 1e0 variants)