Regex for valid Slack usernames

gistfile1.js

// From Slack's interface:
// Usernames may only contain lowercase letters, numbers, periods, 
// dashes and underscores and must start with a letter or number.

/^[a-z0-9][a-z0-9._-]*$/.test(username);

thanks for this!

I've recently seen Slack usernames with spaces and uppercase letters so this may be outdated.

you are right, thanks!