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JavaScript — Interactive Tutorial

A complete JavaScript learning path: five levels from your first program to expert internals. Every lesson has runnable examples, a quiz, and coding challenges — all free.

The whole path

57 of 151 lessons written

Foundations

First Steps
  1. Your First JavaScript Program
  2. Values and Types
  3. Variables: let and const
  4. var and Why It Was Replaced
  5. Numbers and Math
  6. Decimals, Rounding and Precision
Working with Text
  1. Strings and Template Literals
  2. Essential String Methods
  3. Searching, Splitting and Joining
  4. Type Conversion and Coercion
Making Decisions
  1. Booleans and Comparisons
  2. Truthy, Falsy and Nullish
  3. if, else if and else
  4. switch Statements
  5. The Ternary Operator
Loops
  1. while and do...while
  2. for Loops
  3. break and continue
  4. Nested Loops
Functions
  1. Functions: Reusable Code
  2. Returning Values
  3. Function Expressions
  4. Arrow Functions
  5. Default and Rest Parameters
  6. Scope and Shadowing
Craft and Debugging
  1. Comments, Naming and Style
  2. Errors and How to Read Them
  3. Getting Input
  4. Project: Number Guessing Game

Beginner

Arrays
  1. Arrays: Lists of Data
  2. Adding and Removing Items
  3. Looping Over Arrays
  4. map(): Transforming Every Item
  5. filter(): Keeping What Matters
  6. reduce(): Folding to One Value
  7. find, some and every
  8. Sorting Arrays
  9. Array Destructuring
  10. The Spread Operator
  11. Nested Arrays and flat()
Objects
  1. Objects: Named Data
  2. Methods and this
  3. Looping Over Objects
  4. Object Destructuring
  5. Spreading and Merging Objects
  6. Optional Chaining and ??
  7. Working with Nested Data
  8. JSON: stringify and parse
Built-in Objects
  1. Dates and Times
  2. The Math Object
  3. Sets: Unique Values
  4. Maps: Any Key You Like
Functions, Deeper
  1. Callbacks: Functions as Arguments
  2. Closures
  3. Recursion
  4. Pure Functions and Side Effects
  5. try, catch and throw
  6. Custom Error Types
Text and Modules
  1. Template Literals in Depth
  2. Regular Expressions: The Basics
  3. Groups, Flags and Replace
  4. Modules: import and export
  5. Project: To-Do List

Intermediate

The DOM
  1. What the DOM Actually Is
  2. Selecting Elements
  3. Changing Text and HTML
  4. Attributes and Data Attributes
  5. Classes and Styles
  6. Creating and Removing Elements
  7. Moving Around the Tree
  8. Efficient DOM Updates
Events
  1. Listening for Events
  2. Bubbling and Capturing
  3. Event Delegation
  4. Forms and preventDefault
  5. Keyboard and Mouse Events
  6. Custom Events
Asynchronous JavaScript
  1. setTimeout and setInterval
  2. Synchronous vs Asynchronous
  3. Callback Hell
  4. Promises
  5. Chaining Promises
  6. Handling Promise Failures
  7. async and await
  8. Promise.all and Friends
  9. Async Iteration
Talking to the Network
  1. fetch: Getting Data
  2. Sending Data
  3. When Requests Fail
  4. URLs and Query Strings
  5. Storing Data in the Browser
  6. Useful Browser APIs
Classes
  1. Classes
  2. Inheritance with extends
  3. Getters and Setters
  4. Static and Private Members
  5. Debouncing and Throttling
  6. Project: Live Weather App

Advanced

The Object Model
  1. Prototypes
  2. Prototypal Inheritance
  3. What class Really Compiles To
  4. Property Descriptors
  5. Freezing and Copying
Functional JavaScript
  1. Closures in Depth
  2. IIFEs and Scope Isolation
  3. Currying and Partial Application
  4. Function Composition
  5. Memoization
  6. this: The Real Rules
Iteration Protocols
  1. Iterators and Symbol.iterator
  2. Generators
  3. Symbols
  4. WeakMap and WeakSet
  5. Proxy and Reflect
The Runtime
  1. The Event Loop
  2. Modules in Depth
  3. Bundlers and Tree Shaking
  4. Designing for Failure
Browser Platform
  1. Observers
  2. Web Components
  3. Drawing with Canvas
  4. Web Workers
  5. Advanced Regular Expressions
  6. Internationalisation
Patterns and Practice
  1. Design Patterns in JavaScript
  2. Testing Your Code
  3. Project: Kanban Board

Expert

How JavaScript Runs
  1. Parsing, JIT and Bytecode
  2. Execution Contexts
  3. Hoisting and the TDZ
  4. Memory: Heap, Stack, References
  5. Garbage Collection
Performance
  1. Measuring Before Optimising
  2. How Engines Optimise
  3. Rendering Performance
  4. Code Splitting and Lazy Loading
  5. Cancellation and Backpressure
  6. Streams
Security
  1. XSS and Safe Rendering
  2. CORS, CSP and Origins
  3. Prototype Pollution
Mastery
  1. Metaprogramming
  2. Decorators and Wrapping Behaviour
  3. Typed Arrays and Binary Data
  4. WebAssembly Interop
  5. Types Without TypeScript
  6. Testing in Depth
  7. Debugging Like a Professional
  8. Designing APIs Others Enjoy
  9. Reading Someone Else's Code
  10. Capstone: A Complete Single-Page App