Restrict Possible Usernames - reading code wrong

JavaScript
1

Why doesn’t this code work?

The way I am reading it is that:

the first character must be a letter,
the + means the second character must also be a letter
the rest of the code means that the final character can be a number (or not)

What am I reading wrong?

Your code so far


let username = "JackOfAllTrades";
let userCheck = /^[a-z]+\d*$/ig; // Change this line
let result = userCheck.test(username);

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36.

Link to the challenge:
https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/regular-expressions/restrict-possible-usernames

2

Well, the first thing is that [a-z] only catches lowercase letters. If you want uppercase letters too, it’s [a-zA-Z]. Go to regexr.com and paste in your regular expression. At the bottom in the tools section (make sure it’s on the explain part), it will explain your regex. Also, you can find a regex reference and cheatsheet, search for existing regexes under community patterns, and more.

3

Except that his regex is using the /i flag, so it’s case-insensitive.

The /g flag is a problem though – try removing it so the regex is just /^[a-z]+\d*$/i. That will leave you with just one test failing, but you should be able to figure that one out.

1 Like
4

Oh :ok: , sorry. I noticed that case-insensitive thing, but my brain :brain: thought :thinking: it meant case-sensitive for some reason. :roll_eyes: :rofl:

5

The + means “one or more” and the * “zero or more”.
Almost there - with this code (without the g flag) it would be accepted also an username like “A”, but it is against challenge requirements

This is why you shouldn’t be using the g flag:

Using test() on a regex with the global flagSection

If the regex has the global flag set, test() will advance the lastIndex of the regex. A subsequent use of test() will start the search at the substring of str specified by lastIndex ( exec() will also advance the lastIndex property). It is worth noting that the lastIndex will not reset when testing a different string.

1 Like