Query Engine: Your Own where + groupBy
Build a chainable query API over plain arrays so you finally understand the tools, lodash, SQL, LINQ, that you will lean on for the rest of your career.
What you'll be able to build
Build a chainable query API over plain arrays so you finally understand the tools, lodash, SQL, LINQ, that you will lean on for the rest of your career. Along the way you pick up real, transferable JavaScript skills, not just this one project:
- higher-order functions and chaining APIs
- reduce for groupBy and aggregation
- comparator functions and multi-key sort
- method chaining via returning `this`/new instances
- generators for lazy evaluation
- modeling tabular data as objects
A course like this one
Yours is built from your own placement, so module count and depth will differ. This map shows what a advanced-level JavaScript learner building Query Engine actually gets.
- Module 1: Advanced JavaScript Values and Product State5 lessons
Builds the production-ready version of the component state for your query engine.
- Module 2: Advanced Functions, Modules, and Tests5 lessons
Builds the production-ready version of the reusable utility function for your query engine.
- Module 3: Advanced API Boundaries and Async Thinking5 lessons
Builds the production-ready version of the API adapter for your query engine.
- Module 4: Advanced Arrays, Objects, and Client Data5 lessons
Builds the production-ready version of the client data model workflow for your query engine.
- Module 5: Advanced Events, Branches, and UI Decisions5 lessons
Builds the production-ready version of the event rule that powers your query engine.
- Module 6: Advanced Frontend Launch Readiness3 lessons
Builds the production-ready version of the release checklist for your query engine.
How the lessons actually work
Every lesson has you predict what a piece of JavaScript code will output before you run it, then run it for real in your browser and fix what you got wrong. Each module ends in a challenge gate with hidden tests, so you can't advance until your code actually works. The course closes with a capstone that assembles everything into Query Engine, and a runnable proof page tied to your own code.
Common questions
How long does the Query Engine: Your Own where + groupBy course take?
about 7 hours, across 6 modules and 28 lessons, at roughly 15 minutes per lesson. Your own course may run shorter or longer, since it's sized to your placement result, not a fixed template.
Do I need experience?
Yes. This is an advanced-tier JavaScript project, so it assumes you're already comfortable writing and reading JavaScript before you start.
How much does it cost?
$15 one-time, no subscription. The first module is free, so you can see exactly how the course teaches before you pay for the rest.