JavaScript String Interview Questions
String handling comes up in both concept and coding rounds. Here are the common questions.
Are strings mutable in JavaScript?
No — strings are immutable. Every method (slice, replace, toUpperCase) returns a NEW string; the original is unchanged.
What are template literals?
Backtick strings with ${expression} interpolation and multi-line support. Tagged templates let a function process the pieces and values — the basis of styled-components.
`Hi ${name}, you have ${count} items`How do you reverse a string?
Spread into an array, reverse, and join: [...s].reverse().join('') — [...] handles unicode better than split('').
How do you check for a palindrome?
Normalise (lowercase, strip non-alphanumerics), then compare with two pointers from both ends moving inward — O(1) extra space.
How do you check if two strings are anagrams?
Count characters in one pass with a hash map, then compare — O(n), better than sorting both (O(n log n)).
Get the coding patterns
Frequency counter, two pointers, sliding window and the string problems interviewers ask — in the JavaScript Coding Handbook.
⚡ Get the JavaScript Interview Kit → ₹299Frequently asked questions
- replace vs replaceAll?
- replace changes the first match (or all with a /g regex); replaceAll changes all literal matches without needing a regex.
- How do I get the last character?
- str.at(-1) — cleaner than str[str.length - 1].