JavaScript Foundations

A calm tour of the language behind every website. We stay in the browser console for the first hour, then build small pieces of real behaviour: a fetch that handles failure, a debounce you understand line by line, and modules that keep a project tidy.

The route

1. Values, and the console as a lab

   Primitives and objects, and how to interrogate anything before writing a line.

   You board here
   40 min
2. Functions, scope and closures

   What a closure is once you stop being frightened of the word, and where it shows up.

   40 min
3. The methods worth memorising

   map, filter and reduce, destructuring and spread — including when each is the wrong choice.

   40 min
4. Async, honestly

   The event loop, promises and async/await, and what happens to errors in each.

   40 min
5. Modules and a project that stays tidy

   Imports, exports, and how to split a file before it becomes a problem.

   30 min

A look at the teaching

async function getCourse(id) {
  const res = await fetch(`/api/courses/${id}`);

  // fetch only rejects on network failure — a 404 or a 500
  // is a perfectly successful promise with a sad status.
  if (!res.ok) {
    throw new Error(`Course ${id}: ${res.status}`);
  }

  return res.json();
}

Who is driving