File Explorer Tree with Keyboard Navigation

Challenge summary

Build a file explorer tree that sorts folders first, opens and closes folders, selects files, and works fully from the keyboard as an accessible tree widget.

What you'll practice

• Render nested folder data recursively with folders sorted above files.
• Apply tree roles and the expanded and selected states to the right items.
• Move one tab stop with arrow keys, Home and End using a list of visible items.
• Keep focus on a visible item when folders collapse.

What Premium unlocks

Premium unlocks the runnable workspace, behavioral checks, implementation walkthrough, and edge-case discussion.