so I am looking for a regex which disallows two consecutive "." but it can have many. Also the string should not start or end with ".".

I've written a regex but it allows multiple dots consecutively.

new RegExp("^[0-9a-z].*[0-9a-z]$", "i"),

valid examples

"abc.def.hun.asasdsd"
"asasaasass.l"
"p.asasasas"

invalid examples

".asassa"
"sasas..sasas.sas"
"asas.sasas.sasas."
"sasas...sasasdsd.sasass"

CodePudding user response：

You may use this regex:

/^[a-z\d](?!.*\.\.)(?:.*[a-z\d])?$/gmi

RegEx Demo

Explanation:

• ^[a-z\d]: Match alphanumeric char at start
• (?!.*\.\.): Negative lookahead to fail the match if 2 consecutive dots are present anywhere
• (?:.*[a-z\d])?: Match anything followed by alphanumeric char. Make this an optional group match
• $: End

CodePudding user response：

You can use this command, to start with ^[0-9a-z] with the number of letters, and then groups of dot with letters and numbers but not two sequential dots.

const result = new RegExp("^[0-9a-z] ?(\.[0-9a-z] )*$", "i").test('one.dsfsdf.');

console.log(result)

CodePudding user response：

Perhaps this works for your case?

^[0-9a-z] (\.[0-9a-z] )*$

Regex101