I need help understand this regex

JavaScript
1

Continuing the discussion from freeCodeCamp Challenge Guide: Spinal Tap Case:

Here’s the code:

function spinalCase(str) {
  // Replace low-upper case to low-space-uppercase
  str = str.replace(/([a-z])([A-Z])/g, "$1 $2");
  // Split on whitespace and underscores and join with dash
  return str
    .toLowerCase()
    .split(/(?:_| )+/)
    .join("-");
}

// test here
spinalCase("This Is Spinal Tap");

I don’t understand this regrex expression: .split(/(?:_| )+/)

First: what is the question mark before the colon "?: " means? (i couldn’t find in the material);
Second: there’s nothing after the “or” expression “|”, or is that a space after it?
Many thanks.

2

You should get in the habit of researching and tinkering.

Also, regex is weird.

When confronted with regex, I often hop over to a site like regex 101 and mess around with it. You can put in your regex and mess around with it. The “?:” is a bit of an oddball, but if I google “regex ?:”, explanations pop up.

Being able to research and figure things out is a very important skill for a developer. Professional developers are googling things several times a day. I’m an hour into my work day and I have spent at least half of that googling and reading things trying to figure out how to solve my issue.

2 Likes
3

Thank you for your suggestion. Now that I dig deeper into this, I found some problems with all these solutions:

It won’t remove the blank or any other non-word characters at the start of the string. Eg: the string “–This Is Spinal Tap” would return “–this-is-spinal-tap”.
I found the solution to this:

function spinalCase(str) {
  return str
  .replace(/^\W+/, "")
  .split(/\W+|_|(?=[A-Z])/)
  .join("-")
  .toLowerCase();
}

console.log(spinalCase('--This Is Spinal Tap'));
// this-is-spinal-tap
4

We like to obscure working solutions to challenges so I added [spoiler][/spoiler] tags.

Yeah, the possible inputs are not clearly defined, so I agree that your solution is more robust.

Keep in mind that the solutions aren’t very well maintained so you have to take them with a grain of salt. Personally, I wish we’d just get rid of them.

1 Like
5

I agree, I think it would encourage the research and tinkering as you mentioned too, instead of just looking at the solutions and moving on to the next challenge.

6

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