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JavaScript JavaScript Array Iteration Methods Array Manipulation Practice reduce()

Posted by William Bailey
William Bailey
4,585 Points

Would anyone like to check the following code and then explain to me why i'm not getting the correct result?

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
phoneNumbers.reduce((count, value) => {
  const areaCode = value.substr(0,5);
  if (areaCode === '(503)') {
    numberOf503 = count +=1;
  }
  count
}, 0);

2 Answers

Steven Parker
Steven Parker
231,184 Points
Steven Parker
Steven Parker
231,184 Points

The callback function doesn't return anything.

On the line that just has "count" by itself, did you perhaps intend to write "return count;" instead?

Also, the challenge will be expecting you to assign the result of the "reduce" call to "numberOf503" instead of assigning it inside the callback.

William Bailey
William Bailey
4,585 Points
William Bailey
William Bailey
4,585 Points

Thanks so much! The final version of that code is below it was a face-palm once you said that haha. Thanks again.

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((count, value) => {
  const areaCode = value.substr(0,5);
  if (areaCode === '(503)') {
    return count +=1;
  }
  return count;
}, 0);
William Bailey
William Bailey
4,585 Points

The challenge can be solved making the edits above from the original code thanks to Steven's input. :)!~!