freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/regular-expressions/restrict-possible-usernames.md

id, title, challengeType, forumTopicId

id	title	challengeType	forumTopicId
587d7db8367417b2b2512ba2	Restrict Possible Usernames	1	301363

Description

Usernames are used everywhere on the internet. They are what give users a unique identity on their favorite sites. You need to check all the usernames in a database. Here are some simple rules that users have to follow when creating their username. 1) Usernames can only use alpha-numeric characters. 2) The only numbers in the username have to be at the end. There can be zero or more of them at the end. Username cannot start with the number. 3) Username letters can be lowercase and uppercase. 4) Usernames have to be at least two characters long. A two-character username can only use alphabet letters as characters.

Instructions

Change the regex userCheck to fit the constraints listed above.

Tests

tests:
  - text: Your regex should match <code>JACK</code>
    testString: assert(userCheck.test("JACK"));
  - text: Your regex should not match <code>J</code>
    testString: assert(!userCheck.test("J"));
  - text: Your regex should match <code>Jo</code>
    testString: assert(userCheck.test("Jo"));
  - text: Your regex should match <code>Oceans11</code>
    testString: assert(userCheck.test("Oceans11"));
  - text: Your regex should match <code>RegexGuru</code>
    testString: assert(userCheck.test("RegexGuru"));
  - text: Your regex should not match <code>007</code>
    testString: assert(!userCheck.test("007"));
  - text: Your regex should not match <code>9</code>
    testString: assert(!userCheck.test("9"));
  - text: Your regex should not match <code>A1</code>
    testString: assert(!userCheck.test("A1"));
  - text: Your regex should not match <code>BadUs3rnam3</code>
    testString: assert(!userCheck.test("BadUs3rnam3"));
  - text: Your regex should match <code>Z97</code>
    testString: assert(userCheck.test("Z97"));
  - text: Your regex should not match <code>c57bT3</code>
    testString: assert(!userCheck.test("c57bT3"));  

Challenge Seed

let username = "JackOfAllTrades";
let userCheck = /change/; // Change this line
let result = userCheck.test(username);

Solution

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