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Variable

A named container for a value. In JavaScript declared with let (re-assignable) or const (re-assignable to a new value forbidden; the container is fixed, though its contents can mutate for arrays/objects).

let count = 0;
const name = "George";

var is the old, function-scoped declaration — basically never used in modern code.

See also: JavaScript

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Vector (in AI)

A list of numbers representing something — usually text or an image — in a way that captures meaning. An embedding is a vector. Stored in vector databases (Pinecone, Weaviate, Postgres+pgvector) and searched by similarity.

See also: Embeddings, Vector databases, RAG

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Vector database

A specialised database for storing and searching embeddings — the numerical representations of text/images/audio that capture meaning. The infrastructure behind RAG, semantic search, and AI recommendation. Major options: Pinecone (managed), Weaviate (open-source EU), Chroma (simple), Qdrant (Rust/EU), pgvector (Postgres extension). For Australian use: pgvector on Supabase Sydney is often the simplest path.

See also: Vector databases, RAG, Embeddings

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Vercel

A hosting platform built around Next.js (Vercel makes Next.js). Git push triggers a build and deploy automatically. Includes serverless functions, edge functions, image optimization, analytics, and a generous free tier. The default deploy target for new Next.js projects.

See also: Vercel, Next.js

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Version

A specific numbered release of a piece of software. Modern packages follow SemVer (semantic versioning): MAJOR.MINOR.PATCH (e.g. 15.2.4). Bumping MAJOR signals breaking changes; MINOR adds backwards-compatible features; PATCH fixes bugs.

See also: npm, Package

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Virtual DOM

React’s in-memory representation of what the DOM should look like. When state changes, React builds a new virtual DOM, diffs it against the previous one, and applies only the differences to the real DOM. Less critical now that React has compiler optimizations, but historically the whole reason React was fast.

See also: React, DOM

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Vite

A modern bundler/dev server, much faster than the older Webpack-based tools. Used by many React tools (Vitest, Astro, SvelteKit, etc.) under the hood. Next.js doesn’t use Vite directly — it has its own bundler (Turbopack) — but most non-Next React projects do.

See also: Build

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Vitest

A fast test framework built on Vite, with an API very close to Jest. Increasingly replacing Jest in the React/Next ecosystem for new projects.

See also: Jest, Unit tests

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