Day 3: Palindrome in JavaScript – 3 Methods with Simple Explanations

 🚀 Day 3 – Check if a String is a Palindrome (JavaScript DSA)

Hey developers 👋,

Welcome to Day 3 of my JavaScript + DSA Interview Series – Code With Jaffer.

Today, we’re solving a super common and super important problem:

> 🧠 Check if a given string is a palindrome.

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🔍 What is a Palindrome?

A palindrome is a word, phrase, number, or sequence that reads the same forward and backward.

🔤 Examples:

✅ "madam" → Palindrome

❌ "hello" → Not a palindrome

✅ "racecar" → Palindrome

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💡 Problem Statement:

Input: A string

Output: true if it's a palindrome, else false

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✅ Solution 1: Built-in JavaScript Functions

function isPalindrome(str) {

  return str === str.split('').reverse().join('');

}

🧠 Explanation:

split(''): Converts string to array

reverse(): Reverses array

join(''): Combines back into a string

Compares reversed and original

💬 Tips to Remember:

> Split → Reverse → Join → Compare

Use this when you need a quick and clean answer.

⏱️ Time: O(n) | 🧠 Space: O(n)

✅ Best for quick solutions in interviews

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✅ Solution 2: Two-Pointer Approach (Efficient)

function isPalindrome(str) {

  let left = 0;

  let right = str.length - 1;

  while (left < right) {

    if (str[left] !== str[right]) return false;

    left++;

    right--;

  }

  return true;

}

🧠 Explanation:

Set two pointers: start and end

Compare characters from both ends

If mismatch → return false

💬 Tips to Remember:

> “Left meets Right” — simple pointer technique

✅ Use this in coding rounds where performance matters

⏱️ Time: O(n) | 🧠 Space: O(1)

✅ Best for low memory usage

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✅ Solution 3: Recursion (For Logic Practice)

function isPalindrome(str) {

  if (str.length <= 1) return true;

  if (str[0] !== str[str.length - 1]) return false;

  return isPalindrome(str.slice(1, -1));

}

🧠 Explanation:

Base case: 1 or 0 length string → true

Recursive call: compare outer chars, slice and check middle

💬 Tips to Remember:

> Think like onion peeling 🧅 – remove outer layers recursively

⏱️ Time: O(n²) (due to slicing) | 🧠 Space: O(n)

⚠️ Avoid for large strings – good for concept-building

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🧠 Interview Tips:

✅ Use the 2-pointer approach to show algorithmic thinking

✅ Use recursion only if interviewer asks for it

✅ Always explain your logic + complexity clearly