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Cover image for JS Coding Question #3: Is Palindrome [Common Question]
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JS Coding Question #3: Is Palindrome [Common Question]

Interview Question #3:

Write a function that returns if string a palindromeβ“πŸ€”
Palindrome happens when a string forms the same word when it is reversed.

Example:
abba => true
abcba => true
123xyz => false

If you need practice, try to solve this on your own. I have included 2 potential solutions below.

Note: There are many other potential solutions to this problem.

Feel free to bookmark πŸ”– even if you don't need this for now. You may need to refresh/review down the road when it is time for you to look for a new role.

Code: https://codepen.io/angelo_jin/pen/RwgPVwr

Solution #1: Array reverse and join and methods

  • very straight forward solution using array methods.
function isPalindrome(str) {
  return str
    .split('')
    .reverse()
    .join('') === str;
}
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Solution #2: Array forEach

  • iterative solution that avoids array reverse() and join() methods
function isPalindrome(string) {
    // find the length of a string
    const len = string.length

    // loop through half of the string
    for (let i = 0; i < len / 2; i++) {

        // check if first and last string are same
        if (string[i] !== string[len - 1 - i]) {
            return false
        }
    }
    return true
}
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Solution #3: Array every

  • another iterative solution and is shorter version.
function isPalindrome(str) {
  return str.split('').every((char, i) => {
    return char === str[str.length - i - 1]
  })
}
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Happy coding and good luck if you are interviewing!

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Top comments (2)

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filipvartolomei profile image
filip • Edited on

Hello my friend!
One time I had this type of interview exercise, the only problem that it has to be made without using strings!
It was only for numbers.
For example, 121 is palindrome while 123 is not.
It would be nice you put a solution without using strings, maybe to help others who reads this article.

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frontendengineer profile image
Let's Code

I apologize for overlooking this.

a possible solution is that you can use is to convert the number to array right away and then adapt either my two solutions above.

const numberToArray = (number) => {
    var arr = [];
    while(number>0) { arr.push(number%10); number = number/10|0; }
    return arr.reverse();
}```

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