SoftwareTestPilot
LearnCoding RoundsCommunityJobsQA Resources
All questions
BasicJavaScript~8 min

First non-repeating character

Asked in product and service company SDET rounds

Points available

100/100

Your mission

  1. Read
  2. 2Run
  3. 3Submit
  4. 4Solve

Write firstUnique(str) returning the first character that appears exactly once.

Return null if every character repeats.

Examples

firstUnique("automation") → "u"
firstUnique("aabb") → null

Hints

Each hint costs 10 points on a full solve.

Interviewer follow-ups

  • What changes for a stream of characters?

Ctrl+Enter to run · add Shift to submit

1
2
3
4
Tab inserts two spaces. Press Escape, then Tab, to leave the editor.
Terminal

$ node solution.js

Run executes the open file. Submit scores solution.js against hidden tests.

SoftwareTestPilot

Learn QA, prove your skills, connect with testers and grow your career.

Platform
  • Learn
  • Community
  • Jobs
Resources
  • QA Resources
  • Interview Questions
  • QA Tools
  • Articles
  • Products
Company
  • About
  • Contact
  • Authors & Reviewers
  • Editorial Policy
  • Sitemap
© 2026 SoftwareTestPilot. All rights reserved.
Operated by SoftwareTestPilot · Pune, Maharashtra, India · softwaretestingsapiens@gmail.com
PrivacyTermsCookiesDisclaimerRefundsAccessibility