How to write palindrome program using JavaScript

In this tutorial, we are going to learn how to implement palindrome program in JavaScript.

What is Palindrome?

A palindrome is a word or number or phrase which can be read same as backward and forward.

for example: mom, LoL, 11011, 10201 or “A man, a plan, a canal, Panama!“.

Let’s write our function to check is give value is palindrome or not.

Note: we are using regular expression [\W_] to remove the non alpha numeric characters such as `

($ , % , @, !)` . These are alpha (A-Z,a-z) numeric(0-9) characters.

function palindrome(str) {

  // remove the non alpha numeric characters and lower case the string.

  let lowercase = str.replace(/[\W_]/gi, '').toLowerCase()

  // reverse the lower case string

  let stringreverse = lowercase.split('').reverse().join('');

  // compare both lowercase and stringreverse

  if (lowercase === stringreverse) {
    return true
  } else {
    return false
  }
}
console.log(palindrome("A man, a plan, a canal, Panama!"));
// true

• In the above code first, we removed the all non-alphanumeric characters from the string by using regex([/W_]) inside the replace method then we lowercased the string.

• Next step, we reversed the lower case string. (because we need to read the same as backward).

• The final step, we compared both strings and returned true if its palindrome otherwise we return false.

We can also refactor our code in two lines instead of using variables.

function palindrome(str){

   let lowercase =  str.replace(/[\W_]/gi,'').toLowerCase()

  return lowercase  === [...lowercase].reverse().join('')
}