Please let me know what's wrong with the code I wrote

Question

const phoneNumbers = ["(503) 123-4567", "(646) 123-4567", "(503) 987-6543", "(503) 234-5678", "(212) 123-4567", "(416) 123-4567"];
let numberOf503

// numberOf503 should be: 3
// Write your code below
const regex = /\(?503.*/gm

numberOf503 = phoneNumbers.reduce((count, phone) => {
  if(regex.test(phone)) {
    return count += 1
  }
  else {
    return count
  }
}, 0)

console.log(numberOf503);

This is my answer to the challenge. I really don't understand why the console.log is printing 2 instead of 3. Somehow, the last 503 is not being captured ("(503) 234-5678")

app.js

const phoneNumbers = ["(503) 123-4567", "(646) 123-4567", "(503) 987-6543", "(503) 234-5678", "(212) 123-4567", "(416) 123-4567"];
let numberOf503;

// numberOf503 should be: 3
// Write your code below

Answer 1 · 2021-02-01T19:34:41Z

February 1, 2021 7:34pm

When using test() on a RegExp with the global(g) flag, it tracks the lastIndex and starts from there instead of 0. Since you have two 503 numbers back to back, it is missing the second and not counting it! If you remove the g from your regular expression, the code works perfectly!

I'm not great at explaining and had to do some digging myself to even word this answer... However, this stack overflow question goes into better depth than I can!: https://stackoverflow.com/questions/1520800/why-does-a-regexp-with-global-flag-give-wrong-results

I hope this helps!

Answer 2 · 2021-02-03T06:32:26Z

February 3, 2021 6:32am

Ahh, thank you very much Cody. I got it now

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Andy Hartono

Andy Hartono

Please let me know what's wrong with the code I wrote

2 Answers

Cody Hansen

Cody Hansen

Andy Hartono

Andy Hartono