Glossary — E
Back to glossary index · Master INDEX
Edge (functions, edge network)
Code that runs on servers physically close to the user, rather than in one central location. Vercel and Cloudflare both run “edge” networks with hundreds of points of presence around the world. Edge functions are perfect for tasks that need low latency (header rewrites, A/B test routing) but they have constraints — typically no Node.js APIs, smaller bundle sizes, shorter time limits.
See also: Edge functions, CDN, Serverless
Embedding
A numeric representation of text (or images, or audio) as a vector — typically a list of 768, 1024, or 1536 floating-point numbers. Two pieces of text that mean similar things will have vectors that are mathematically close to each other. The foundation of RAG, semantic search, and many other AI applications.
See also: Embeddings, Vector database, RAG
Endpoint
A specific URL on a server that an API responds to. POST /api/users is an endpoint. GET /api/users/:id is another. Combining the method (GET/POST/etc.) and the path uniquely identifies an endpoint.
Environment (env, environment variable)
Two related meanings. Environment in the broad sense: the context an app is running in — development on your laptop, staging server, production. Environment variables are configuration values that change per environment — e.g. DATABASE_URL points to one database locally and a different one in production. Stored in .env files locally, in the hosting provider’s dashboard for production.
See also: Environment variables
Error
A signal that something has gone wrong. In JavaScript, errors are thrown (throw new Error("...")) and caught with try/catch. Reading error messages carefully — instead of skimming and panicking — is the single most underrated debugging skill.
See also: Debug, JavaScript
ES Modules (ESM)
The modern, standard module system for JavaScript. Use import and export keywords. The older system was CommonJS (require() and module.exports), still used in older Node.js code. Modern Next.js, browsers, and Node 20+ all support ESM natively.
// ESM
import { useState } from "react";
export function Counter() { ... }
// CommonJS (older)
const { useState } = require("react");
module.exports = { Counter };Event
Something that happens that code can react to. In the browser: clicks, key presses, scrolls, form submissions, network responses. In Node: incoming HTTP requests, file changes, timer firings. You attach an event handler (or “event listener”) that runs when the event happens.
button.addEventListener("click", () => alert("clicked!"));See also: JavaScript, The DOM
← D · Glossary index · F →