Get all email addresses in a string
$ npm install get-emails
import getEmails from 'get-emails';
const text = 'Lorem ipsum dolor, sindresorhus@gmail.com consectetuer unicorn@rainbow.cake elit.';
getEmails(text);
//=> Set {'sindresorhus@gmail.com', 'unicorn@rainbow.cake'}
If the string comes from user input, it's up to you to limit it to some reasonable length to prevent abuse.