Working with Regular Expressions - What Are Capturing Groups and Backreferences, and How Do They Work?

rasikarsw · April 5, 2025, 12:12am

Tell us what’s happening:

const regex = /free(co+de)camp.*free(co+de)camp/i;
console.log(regex.test(“freecooooodecamp is great i love freecooooodecamp”)); // true
console.log(regex.test(“freecooooodecamp is great i love freecodecamp”)); // false

I discovered an error in the transcript; the second console log output a true result. Furthermore, the lecture video (3:18) has a different code snippet compared to the transcript.

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Working with Regular Expressions - What Are Capturing Groups and Backreferences, and How Do They Work?

a1legalfreelance · April 5, 2025, 7:35am

It would be great if you can report this to help make FCC better. Bugs can be reported as GitHub Issues. Whenever reporting a bug, please check first that there isn’t already an issue for it and provide as much detail as possible.

jwilkins.oboe · April 8, 2025, 3:41pm

I have created an issue for it here

github.com/freeCodeCamp/freeCodeCamp

Incorrect code example used in Regex backreferences lecture

opened 03:39PM - 08 Apr 25 UTC

jdwilkin4

help wanted scope: curriculum full stack cert

Here is the lecture https://www.freecodecamp.org/learn/full-stack-developer/lec…ture-working-with-regular-expressions/what-are-capturing-groups-and-backreferences-and-how-do-they-work In the transcript, we have the following description and code example: ````md Inside a regular expression, a backreference is denoted with a backslash followed by the number of the capture group: ```js const regex = /free(co+de)camp.*free(co+de)camp/i; console.log(regex.test("freecooooodecamp is great i love freecooooodecamp")); // true console.log(regex.test("freecooooodecamp is great i love freecodecamp")); // false ``` And with that, we can see that a string with the correct number of os matches, while a string with two different numbers of os does not. ```` That second log will be true. But also, it doesn't match up with the surrounding text. The original script as well as video have the correct code which is this ````md Inside a regular expression, a backreference is denoted with a backslash followed by the number of the capture group: ```js const regex = /free(co+de)camp.*free\1camp/i; console.log(regex.test("freecooooodecamp is great i love freecooooodecamp")); // true console.log(regex.test("freecooooodecamp is great i love freecodecamp")); // false ``` And with that, we can see that a string with the correct number of `o`s matches, while a string with two different numbers of `o`s does not. ````

The video has the correct code but the transcript, as you pointed out, does not.

Thanks for catching this

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Working with Regular Expressions - What Are Capturing Groups and Backreferences, and How Do They Work?

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