Question 1

Build a Dropdown Menu

Accepted Answer

**Target Audience:** Frontend candidates preparing for a machine coding round. Assumes basic HTML, JavaScript and React components with `useState`; everything else is explained here. **Difficulty:** Easy > **How to read this doc:** Each idea is explained in plain words first, then tagged with 📌 Interview term: so you also learn the vocabulary an interviewer listens for. Every output quoted below was printed by the real solution, run on React 19.3.1 in jsdom and again in real Chrom

Question 2

Build dependent (Country–State) dropdowns

Accepted Answer

**Target Audience:** Frontend candidates preparing for a machine coding round. You know a little HTML and JavaScript; no React form experience is assumed. **Difficulty:** Medium > **How to read this doc:** Every idea is explained in plain language first, then tagged with 📌 Interview term: so you also learn the exact words an interviewer listens for. Code excerpts are copied from the runnable solution, and the output in section 6 was produced by actually running it on React 19.3.1

Question 3

Build a Search Bar with History

Accepted Answer

**Target Audience:** Frontend developers preparing for a machine coding round. Assumes basic React state and events; `localStorage` and focus management are explained from zero. **Difficulty:** Medium > **How to read this doc:** Every idea is explained in plain language first, then tagged with 📌 Interview term: so you also learn the exact words an interviewer listens for. The Verified output was produced by running the solution on React 19.3.1 in jsdom, with a driver that typed, p

Question 4

Build an Autocomplete / Typeahead search

Accepted Answer

**Target Audience:** Frontend developers preparing for a machine coding round. Assumes basic React state and effects; keyboard navigation, caching and ARIA roles are explained from zero. **Difficulty:** Medium > **How to read this doc:** Every idea is explained in plain language first, then tagged with 📌 Interview term: so you also learn the exact words an interviewer listens for. The Verified output was produced by running the solution on React 19.3.1 in jsdom with a scripted dri

Question 5

Build a Custom Multi-select Dropdown

Accepted Answer

**Target Audience:** Frontend developers preparing for a machine coding round. Assumes React state and props; sets, chips, focus handling and multi-select ARIA are explained from zero. **Difficulty:** Medium > **How to read this doc:** Every idea is explained in plain language first, then tagged with 📌 Interview term: so you also learn the exact words an interviewer listens for. The Verified output was produced by running the solution on React 19.3.1 in jsdom with a driver that cl

Question 6

Build a Data Table with sorting and filtering

Accepted Answer

**Target Audience:** Developers preparing for a frontend machine coding round who know React state and lists and want to build a correct, reusable sortable and filterable table. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Code excerpts are copied from the runnable solution, and the Verified section quotes what it printed on React 19.3.1 while a script clicked headers, typed and changed filters. ## 1. Why This Even Matt

Question 7

Build an E-commerce Product Filter grid

Accepted Answer

**Target Audience:** Developers preparing for a senior frontend machine coding round. Assumes React state, effects and list rendering; the derived-state ideas are explained from scratch. **Difficulty:** Hard > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Code excerpts are copied from the runnable solution, and the Verified section quotes what it printed on React 19.3.1 while a script ticked filters, typed prices and removed chips. The catalogue

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