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JavaScript JavaScript Array Iteration Methods Array Manipulation Practice reduce()

Posted by MIHA W.LEE
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MIHA W.LEE
PHP Development Techdegree Graduate 25,452 Points

Reduce method

I dont why this doesnt work, I think its close to success. Hope someone can help me out, thank you so much!!

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((count,number) => {
       if(number.charAt(0,5) == '(503)'){
          count+1;
       }
});
MIHA W.LEE
.a{fill-rule:evenodd;}techdegree seal-36
MIHA W.LEE
PHP Development Techdegree Graduate 25,452 Points

Thank you so much!

1 Answer

Steven Parker
Steven Parker
231,272 Points
Steven Parker
Steven Parker
231,272 Points

You're getting close, but you have a few issues yet:

  • "charAt" returns only one character, did you perhaps mean to use "slice"?
  • the "+" operator adds without changing the operand, the "+=" operator adds and assigns
  • the callback function needs to return the result
  • the "reduce" needs an explicit numeric starting value, since the array contains strings
MIHA W.LEE
.a{fill-rule:evenodd;}techdegree seal-36
MIHA W.LEE
PHP Development Techdegree Graduate 25,452 Points

Ok, thank you so much! I still confuse about the return keyword, I mean when you should use the return keyword?

Steven Parker
Steven Parker
231,272 Points
Steven Parker
Steven Parker
231,272 Points

Place "return count;" at the end of the callback function (after the "if" block).