Palindromes in Javascript

Question

My goal is to take each word and compare it to the reverse. The code moves nicely until the forEach() loop. Trying word === word.reverse() doesn't work, but hopefully you get the idea. I want to compare the word to the reversed version to find the Palindromes. I realize there are ways to do this only using filter, but the goal is to do it with forEach(). Any suggestions to a simple fix to this is appreciated. Thanks!

//************************* Finding  Palindromes******************/

let arr = "I love Mom she, she is radar mom?"

function pallindromes(arr){
if(arr.length == 0) return console.log(null)the Pa

arr = arr.toLowerCase()
arr = arr.replace(/[?,]/g,"")
arr = arr.split(" ")
arr = [...new Set(arr)]
let newList = []

arr.forEach(word=>{
    if(word === word.reverse()){
        newList.push(word)
    }
})
return console.log(newList)
}

pallindromes(arr)

Should be an error in the console. A string does not have reverse method. — epascarello, Jul 20 '21 at 15:46
And you have some error with the line `return console.log(null)the Pa` — epascarello, Jul 20 '21 at 15:47

score 1 · Accepted Answer · answered Jul 20 '21 at 15:47

changed : word.split("").reverse().join("")

let arr = "I love Mom she, she is radar mom?"

function pallindromes(arr) {
  if (arr.length == 0) return console.log(null);

  arr = arr.toLowerCase()
  arr = arr.replace(/[?,]/g, "")
  arr = arr.split(" ")
  arr = [...new Set(arr)]
  let newList = []

  arr.forEach(word => {
    if (word === word.split("").reverse().join("")) {
      newList.push(word)
    }
  })
  return console.log(newList)
}

pallindromes(arr)

score 0 · Answer 2 · answered Jul 20 '21 at 15:52

0

String does not have a reverse method, but array does.

So replace word.reverse() with word.split("").reverse().join("").

This will make an array, splitting the word on every letter, reverse it, and join it again.

answered Jul 20 '21 at 15:52

0TTT0

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score 0 · Answer 3 · answered Jul 20 '21 at 15:53

What you want is actually a way to reverse a string in Javascript, because .reverse() is only usable for arrays. A lot of posts and questions cover that.

If I take this answer, I can reverse a string with s.split("").reverse().join("");, so by applying this to your code we get

let arr = "I love Mom she, she is radar mom?"
  
function pallindromes(arr){
  if(arr.length == 0) return console.log(null)
 
  arr = arr.toLowerCase()
  arr = arr.replace(/[?,]/g,"")
  arr = arr.split(" ")
  arr = [...new Set(arr)]
  let newList = []

  arr.forEach(word=>{
    if(word === word.split('').reverse().join('')){
      newList.push(word)
    }
  })
  return console.log(newList)
}
  
pallindromes(arr)

returning [ 'i', 'mom', 'radar' ]

I would still advise creating a reverseString() function, so that people not used to javascript can still easily read your code without having to guess what .split().reverse().join() does.

Cheers.

Palindromes in Javascript

3 Answers3