Web development

Split code into modules with named and default exports, use modules in the browser, and dynamic import.

Global, function and block scope, hoisting of declarations, and why let and const throw before declaration.

Throw and catch errors, error types, custom error classes, and handling async errors.

How functions remember their surrounding scope, practical uses, and common closure bugs.

Class syntax, constructors, methods, private fields, static members and extends.

How this is decided at call time, in methods, callbacks, arrow functions and with bind, call and apply.

Transform and search arrays with built-in methods, chaining, and which methods mutate.

Unpack arrays and objects, copy and merge with spread, and collect arguments with rest.

Object.keys, values and entries, shallow versus deep copies with structuredClone, and Object.freeze.

Read nested data safely with ?. and supply defaults with ?? without treating 0 and empty strings as missing.

Convert between objects and JSON text, handle parse errors, and what JSON cannot represent.

The Date object and its pitfalls, formatting dates, numbers and currencies with Intl, and the Temporal API.

Create arrays, read and change elements, add and remove items, and check length.

Create objects, read and update properties, methods, and bracket notation for dynamic keys.

What the DOM is, and selecting elements with querySelector, querySelectorAll and getElementById.

Update text, attributes, classes and styles safely, and why textContent beats innerHTML for user data.

Listen for clicks, input and keyboard events, the event object, and preventDefault.

What JavaScript does in the browser and on servers, how it relates to HTML and CSS, and what ECMAScript means.