Turning a string into an array and saving it as a new array, doesn't return original array

Question

This function cleans up a string (removes all non-alphanumeric characters including underscores) then splits each letter into an array so that it can be reversed, then checked against the original.

At console.log(cleanStr) , it is returning the reversed array but I do not know why.

function checkIfPalindrome(str) {
  var cleanStr = str.toLowerCase().replace(replace, "" ).split("");
  var reversedStr = cleanStr.reverse();

  console.log(cleanStr); // why is this returning reverseStr, the reversed array? 

  if (cleanStr == reversedStr){
     return true
   }
  return false
}

checkIfPalindrome("five|\_/|four");

brunnerh · Accepted Answer · 2018-03-24 15:08:57Z

3

The reverse() method reverses an array in place - it mutates the array it's called on. Try creating a new array instead:

const cleanStr = str.toLowerCase().replace(replace, "" ).split("");
const reversedStr = [...cleanStr].reverse();

edited Mar 24, 2018 at 15:08

brunnerh

188k30 gold badges362 silver badges434 bronze badges

answered Mar 24, 2018 at 15:07

CertainPerformance

373k55 gold badges354 silver badges359 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

T.J. Crowder · Accepted Answer · 2018-03-24 15:08:54Z

At console.log(cleanStr) , it is returning the reversed array but I do not know why.

Because reverse reverses it in place.

Separately, you have a problem here:

if (cleanStr == reversedStr){

If they were different arrays, that would always be false, even if they had the same contents.

If you want to make a copy of the array and then reverse it, throw a .slice() in there:

var reversedStr = cleanStr.slice().reverse();
// -----------------------^

...and then compare after turning them back into strings:

if (cleanStr.join("") === reversedStr.join(""))

(I'd probably change those variable names, too, as they don't refer to strings.)

And finally, any time you find yourself writing:

if (x == b) {
    return true;
}
return false;

back up and write

return x == b;

instead. :-)

Collectives™ on Stack Overflow

Turning a string into an array and saving it as a new array, doesn't return original array

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related