HTML provides structure and meaning; CSS controls presentation and layout. Semantic HTML Use elements that describe content: header, nav, main, article, section, footer, button and form elements. Semantic markup improves accessibility and search engine understanding. Forms Use labels for every input, appropriate input types and built-in validation attributes. CSS essentials Selectors and specificity. The box […]

JavaScript makes pages interactive and also runs on servers. Core concepts Variables with let and const. Data types: strings, numbers, booleans, arrays and objects. Functions, including arrow functions. Control flow with conditions and loops. Array methods such as map, filter and reduce. The DOM The Document Object Model represents the page. JavaScript can select elements, […]

Front-end frameworks help build complex interfaces from reusable components. Components A component combines structure, style and behaviour for part of the interface, such as a task item. Components receive data through properties and manage their own state. State management State is data that changes over time. Keep state as close as possible to where it […]

The back end stores data, enforces business rules and exposes APIs for the front end. REST API design Use nouns for resources: /tasks, /tasks/42. Use HTTP methods for actions. Return appropriate status codes. Use JSON for request and response bodies. Version the API when making breaking changes. Server frameworks Frameworks handle routing, request parsing, middleware […]

Applications need to store data reliably. Relational databases Store data in tables with rows and columns. Relationships use foreign keys. SQL queries select, insert, update and delete data. Relational databases enforce structure and support transactions. Document databases Store flexible JSON-like documents. Useful when data structures vary, but relationships need more care. Modelling Identify entities such […]

Web applications must protect users and data. Authentication Hash passwords with a strong, slow algorithm designed for passwords; never store plain text. Use sessions with secure cookies or tokens. Offer multi-factor authentication for sensitive applications. Authorisation Check on the server that the user is allowed to access or change each resource. Common vulnerabilities Injection attacks. […]

A working application must be tested and deployed reliably. Testing Unit tests for functions and components. Integration tests for API endpoints with a test database. End-to-end tests for critical user journeys. Continuous integration Run tests automatically on every push to a shared repository. Deployment options Platform services, containers or virtual machines. Platform services are simplest […]