freeCodeCamp/guide/english/certifications/javascript-algorithms-and-data-structures/regular-expressions/restrict-possible-usernames/index.md

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Restrict Possible Usernames

Restrict Possible Usernames

Solution:

let username = "JackOfAllTrades";
const userCheck = /^[a-z]([0-9]{2,}|[a-z]+\d*)$/i;
let result = userCheck.test(username);

Explain:

1. ^ - start of input
2. [a-z] - first character is a letter
3. [0-9]{2,0} - ends with two or more numbers
4. | - or
5. [a-z]+ - has one or more letters next
6. \d* - and ends with zero or more numbers
7. $ - end of input
8. i - ignore case of input