Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript JavaScript Array Iteration Methods Array Manipulation Practice reduce()

Samuel Kleos
seal-mask
.a{fill-rule:evenodd;}techdegree
Samuel Kleos
Front End Web Development Techdegree Student 13,307 Points

Why doesn't parseInt(number).toString() work?

Here is my initial solution:

numberOf503 = phoneNumbers.reduce((acc, phone) => (parseInt(phone).toString().substring(0, 3) === "503")? acc+1 : acc, 0);

Here is the solution that worked

numberOf503 = phoneNumbers.reduce((acc, phone) => (phone.substring(1, 4) === "503") ? acc+1 : acc, 0);
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
Rich Donnellan
Rich Donnellan
Treehouse Moderator 27,696 Points

I updated the question with code formatting hinting and fixed a typo in the title.

1 Answer

Steven Parker
Steven Parker
231,172 Points

Since all the phoneNumbers begin with a parenthesis, which is not a digit, then parseInt returns NaN.
That of course does not match "503".