DeepFrontend
Practice ArenaBlogSign in
Go Pro
DeepFrontend

Interview-grade learning paths and hands-on practice for mid-to-senior engineers. Master internals, patterns, and system architecture with runnable code.

All systems operational

Core Courses

  • -JavaScript Internals
  • -React Reconciliation
  • -TypeScript rigor
  • -Next.js Caching
  • -Node.js Event Loop
  • -System Design
  • -Web Security
  • -CSS & Page Layouts

Explore

  • Learning Paths
  • Practice Arena
  • Pricing Options
  • HTML Sitemap

Resources

  • Privacy Policy
  • Terms of Service
  • Email Support

© 2026 DeepFrontend. All rights reserved.

Expert learning environments for web engineering teams.

← All challenges
warmup10 min

Implement range(start, end, step)

Implement range(start, end, step)

Write a lodash-style range supporting three call shapes:

  • range(end) — 0 up to (not including) end.
  • range(start, end) — start up to (not including) end.
  • range(start, end, step) — stepping by step (which may be negative, to count down).
range(5);       // [0, 1, 2, 3, 4]
range(2, 5);    // [2, 3, 4]
range(5, 1, -1); // [5, 4, 3, 2]

Run your code to see results.

Stuck? This challenge exercises:

javascript.data-structures