Full stack development: MERN

Sefism.

A to Z

Glossary

Every concept in this sheet, plus the smaller terms it uses. Select a concept to open its card.

C
Components and props
A React component is a function that returns JSX.
D
DOM, events and fetch
The DOM is the page as a tree of objects that scripts can read and change.
E
Effects and useEffect
useEffect runs after render to synchronise with something outside React, such as a subscription, a timer or a browser API, and returns a cleanup function.
Event loop
JavaScript runs one piece of code at a time.
F
Fetching API data in React
A Vite React app loads data from your API in the browser.
Flexbox, Grid and responsive layout
Flexbox lays items out in one direction, Grid in rows and columns.
Forms and validation
Inputs are controlled by state or read from FormData on submit.
G
Git branches and pull requests
A branch is a cheap pointer to a line of commits.
H
How a request reaches a server
The browser resolves the domain with DNS, opens a connection, negotiates TLS for HTTPS and sends an HTTP request.
HTTP methods and status codes
Methods say what to do (GET read, POST create, PUT replace, PATCH update, DELETE remove).
J
JavaScript essentials
Use const by default and let when reassigning, compare with ===, and use ?? for defaults when 0 or "" are valid.
N
npm, package.json and lockfiles
package.json lists dependencies and scripts; package-lock.json pins exact versions of the whole tree.
P
Promises and async/await
A promise represents a value that arrives later.
R
Routing
Mapping URLs to screens.
S
Semantic HTML and forms
Use elements for their meaning (main, nav, button, a, headings in order) and give every input a label, the right type, name and autocomplete.
State and useState
useState gives a component a value that survives re-renders and a setter that triggers one.
V
Vite dev server and API proxy
Vite serves the React app in development with instant reloads and builds static files for production.
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