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JavaScript JavaScript Array Iteration Methods Array Manipulation Practice reduce()

Posted by John Shockey
John Shockey
45,061 Points

Stuck on using .reduce()

QUESTION: phoneNumbers is array of 10 digit phone numbers, where the first three digits, in parentheses, are area codes. Using reduce, return the total phone numbers with a 503 area code. Store the total in the variable numberOf503.

Can't seem to figure this out using .reduce(); Please help!

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
numberOf503 = phoneNumbers.reduce(function (allNums, num) { 
  if (num.substring(0,5) === '(503)') {

  }
}, 0);

1 Answer

Steven Parker
Steven Parker
229,644 Points
Steven Parker
Steven Parker
229,644 Points

You've got a good start there. Now you just need to increment the total when the "if" is true, and return the total in all cases.

John Shockey
John Shockey
45,061 Points

Got it now! Thanks.