A palindrome is a word or sentence that's spelled the same way both forward and backward, ignoring punctuation, case and spacing.

2A33a2, 2A3 3a2, 2_A33#A2, racecar, RaceCar, and race CAR should all return true.

We have a function named palindrome which passes a str parameter.

First, we replace all the non alphanumeric characters in the string

str = str.replace(/[^0-9a-z]/gi, '');

and turn all the characters in the string to lower case

str = str.toLowerCase();

Which can all be placed on a single line like so

str = str.replace(/[^0-9a-z]/gi, '').toLowerCase();

Next, we need to set a new variable with the string in reverse. First we split the string into an array of characters

let strRevArray = str.split('');

then we reverse the array

let strRevArrayReverse = strRevArray.reverse();

then we join the reversed array back into a string

let strRev = strRevArrayReverse.join('');

Again, all of this could be done in one line

let strRev = str.split('').reverse().join('');

Finally, we check to see if str is equal to strRev and return true if it is and false if it isn't. You could use an if else statement, but the easiest shorthand would be to use ternary

return(str == strRev);

the full code

function palindrome(str) {
  str = str.replace(/[^0-9a-z]/gi, '').toLowerCase();
  let strRev = str.split('').reverse().join('');
  return (str == strRev);
}