i try to catch an input of a field via javascript.

i need to get max 3 numbers and one dot.

i tried this regex: [^\d{0,3}.{0,1}\d{0,3}]

but it isn't quite working, i can't really get how to fetch the numeric values globaly so it is really max 3 numbers.

333   //ok
333   //ok
33.1  //ok
3.33  //ok
3.3.  //not ok
3.333 //not ok
3333. //not ok
3..   //not ok
.     //not ok

Hope someone can give me a hint here.

CodePudding user response：

I am very bad in regex but came up with something like this below. Probably there is a much more elegant way but....

^\d{0,3}$|^\d{2}[.]\d{1}$|^\d{1}[.]\d{1,2}$

Works for MAX 3 numbers so 3 and 33 is also ok

CodePudding user response：

For on-submit (final) validation, you can use

^(?=.{3,4}$)\d (?:\.\d )?$

See the regex demo. It matches

• ^ - start of string
• (?=.{3,4}$) - this requires the string to have three or four chars only
• \d (?:\.\d )? - one or more digits, and then an optional occurrence of a . and one or more digits. As \d, \. and \d are obligatory to match at least once, the min limit as 3 is justified and since only one dot can be matched, either of \d can match one or two digits, but only three all in all
• $ - end of string.

For live input text validation, you can use

^(?:\d{1,3}|\d(?:\d?\.\d?|\.\d{2}))$

See the regex demo. Details:

• ^ - start of string
• (?: - start of a group:
  • \d{1,3} - one, two or three digits
• | - or
  • \d - a digit
  • (?:\d?\.\d?|\.\d{2}) - a non-capturing group matching either
    • \d?\.\d? - an optional digit, a . and then an optional digit
    • | - or
    • \.\d{2} - . and then two digits
• ) - end of the group
• $ - end of string.

CodePudding user response：

You might also match all 3 variations in a non capture group:

^(?:\d{3}|\d\.\d\d|\d\d\.\d)$

Regex demo

Or first match a single digit followed by 2 variations of an optional dot and 2 digits or a single digit, optional dot and a single digit:

^\d(?:\.?\d\d|\d\.?\d)$

Regex demo