A regex is needed which should have only special character dot which should either be optional or occur only once.

pattern = /^([A-Za-z.] )$/;

CodePudding user response：

Without more information I'd use

/^(?!$)[a-z]*\.?[a-z]*$/i

The negative lookahead prevents empty matches.

See this demo at regex101

CodePudding user response：

Here are some ways to do it:

1. Deal separately where the input has has one dot, with optional letters surrounding it, or no dot (but then having at least one letter):

   /^([a-z]*\.[a-z]*|[a-z] )$/i

2. Just capture letters and dots like you did, but don't allow the input to have two dots, using a negative look ahead:

   /^(?!(.*\.){2})([a-z.] )$/i

3. Capture optional letters then an optional point and then optional letters, but forbid an empty input with a negative look-ahead:

   /^(?!$)([a-z]*\.?[a-z]*)$/i