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I am trying to add 2 to given array. But the code returns undefined when run. I am trying to learn ES6, I couldn't find the problem. I need help.

const mapSomething = (arr) => {
  arr.map(n => {
    return n + 2;
    
  })
}

// It have to return [3, 4, 5] but it returns undefined
console.log(mapSomething([1, 2, 3]));
Faruk Şirket
  • 3
  • 1

3 Answers3

0

It is logging undefined because the function is not returning any value.

You have to return the result from Array.map:

const mapSomething = (arr) => {
  return arr.map(n => {
    return n + 2;
  })
}

// It have to return [3, 4, 5] but it returns undefined
console.log(mapSomething([1, 2, 3]));

Also take note that the return statement in your arrow function is redundant, since there is only one expression being evaluated:

const mapSomething = (arr) => {
  return arr.map(n => n + 2)
}

// It have to return [3, 4, 5] but it returns undefined
console.log(mapSomething([1, 2, 3]));
Spectric
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0

You don't have a return statement in the function, so it returns undefined by default.

If an arrow function is a single expression that you want to return, you shouldn't put {} around it. That makes it a normal function body, which requires an explicit return statement (like you have with n + 2).

const mapSomething = (arr) => arr.map(n => n + 2);

// It have to return [3, 4, 5] but it returns undefined
console.log(mapSomething([1, 2, 3]));
Barmar
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0

const mapSomething = (arr) => {
    const arrData = arr.map(n => {
      return n + 2;     
    })

    return arrData
  }
  
  // It have to return [3, 4, 5] but it returns undefined
  console.log(mapSomething([1, 2, 3]))
  
  //NOTE: you where not returning anything from the function itself
skillz TheProgrammer
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