Public JavaScript challenges shared by the EraCode community. These pages are teasers — skill maintenance starts when you attempt the full problem inside EraCode.
Quick check on array collections: when to choose different built-ins, then implement a tiny utility to remove duplicates without reordering.
A quick performance-focused check: recognize when O(1) lookups beat repeated linear scans, then implement a tiny optimization in code.
Quick practice on efficient DOM rendering: batch-create nodes off-screen, then paint once.
A quick performance-focused check-in: avoid unnecessary layout/reflow by batching DOM insertions.
Practice a small JavaScript accessibility pattern: move keyboard focus to an error summary after validation so screen reader and keyboard users get immediate context.
Quick check-in on JavaScript testing: understand when to use a spy and implement a tiny Jest assertion to verify call arguments.
Quick practice on JavaScript data structures: using Map for frequency counting, plus a short concept check.