javascript - Changes in .forEach() have no effect?

Question

So let me preface this with the fact that I'm doing this coding in Codecademy so maybe its just that being weird.

I am trying to remove all punctuation from an array (dupBW) and set everything to lowercase.

My code works fine within the forEach, the console.log shows that. But then dupBW is unaffected when I log it out at the end.

Thanks for the help.

  dupBW.forEach(dupWord => {
    if(puncArray.includes(dupWord[dupWord.length-1])) {
      dupWord = dupWord.slice(0, dupWord.length-1);
      dupWord = dupWord.toLowerCase();
      console.log(dupWord);
    }
  });
  
  console.log(dupBW.join(' '));

Answer 1

Change forEach to map and return dupWord at the end, and it will work; by assigning the array to the newly returned one. Array.prototype.map returns a new array with the return values of the callbacks.

dupBW = dupBW.map(dupWord => {
    if(puncArray.includes(dupWord[dupWord.length-1])) {
      dupWord = dupWord.slice(0, dupWord.length-1);
      dupWord = dupWord.toLowerCase();
      console.log(dupWord);
    }
      return dupWord;
  });
  
  console.log(dupBW.join(' '));