JavaScript: From First Values to Reliable Programs

JavaScript runs in the browser and can make a page respond to people. Here you will learn the language itself first: calculate values, choose what happens next, organize data, and coordinate work that finishes later. The built-in editor lets you run each example without installing anything.

What you will learn

• Core language fundamentals: values, variables, operators, and control flow.
• Functions — how to define, call, and compose them.
• Arrays and objects — the two data structures you will use every day.
• Built-in helpers for strings, numbers, dates, and math.
• Functional patterns: map, filter, reduce, and recursion.
• Object-oriented programming with ES6 classes and inheritance.
• Asynchronous JavaScript: callbacks, Promises, and async/await.

Course outline

1. Introduction — run your first script and inspect values and types in the Console.
2. Variables and Operators — name values, update totals, convert text to numbers, and fix a calculation.
3. Control Flow — choose a path with conditions and repeat work with loops.
4. Functions — turn repeated steps into reusable jobs, then explore scope and closures.
5. Arrays — keep ordered collections, find entries, and transform lists.
6. Objects and Built-ins — name related facts and work with Map, Set, numbers, JSON, math, and dates.
7. Strings and Regular Expressions — prepare messages and validate text patterns.
8. Functional Programming — pass functions as values and combine transformations into a pipeline.
9. Object-Oriented Programming — give objects behavior, then build classes with inheritance and private state.
10. Asynchronous JavaScript — understand delayed work, await Promises, combine independent results, and retry failures.

After this course, continue with a dedicated JavaScript DOM course to learn browser interactivity, or move into Node.js and frameworks like React.

How to work through the lessons

Start with a tiny connection between an HTML page and script.js. After that first lesson, write JavaScript in script.js and check its output in the Console; this course does not ask you to edit page elements. Each section starts with a concrete problem, shows a runnable example, and lets you use the idea in a different exercise. The situations change—from a scoreboard to reservations, records, and deliveries—but the same language skills carry forward. Work through each section in order: later tasks reuse earlier ideas. The asynchronous section uses an offline preview to capture delayed Console output; its sample services do not make network requests.

Intentionally later

This beginner course includes the built-ins you will use regularly for application logic: arrays, objects, Map, Set, Number, BigInt, JSON, Math, and Date. ArrayBuffer is for low-level binary data and belongs in a later browser or data-processing course. eval() executes a string as code, so it is intentionally not taught as a tool for application code; write direct functions and data transformations instead.