CODEWITHSUNDEEP
javascriptregex
localhost
localhost

Reputation: 861

Making dot optional with limited characters

I am trying the following Regex and It is failing

/^\d{1,18}[.]?$/

I want digit 1-18 but a optional dot(.) anywhere. I tried the following too

  /^[1-9]{1,18}[.]?$/

It counts . as a character as well i.e 12345678901234567.

How can I achieve 18 digits and an optional . anywhere in regex

Upvotes: 0

Views: 37

Answers (2)

anubhava
anubhava

Reputation: 785196

You may use this regex with a lookahead to block 2 dots:

^(?!(?:\d*\.){2})[.\d]{1,18}$

RegEx Demo

RegEx Details:

  • ^: Start
  • (?!(?:\d*\.){2}): Negative lookahead to disallow 2 dots
  • [.\d]{1,18}: Match dot or digit for length range between 1 to 18
  • $: End

Upvotes: 3

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626896

You may use

^(?=(?:\.?\d){1,18}\.?$)\d*\.?\d*$

See the regex demo

Details

  • ^ - start of string
  • (?=(?:\.?\d){1,18}\.?$) - a positive lookahead that requires 1 to 18 occurrences of an optional . and any digit followed with an optional . at the end of string
  • \d*\.?\d* - 0+ digits, an optional . and again 0+ digits
  • $ - end of string.

Upvotes: 1

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