What is JavaScript?
The programming language of the web, running in every browser and, via Node.js, on servers.
Definition
JavaScript is a dynamically typed, single-threaded language standardized as ECMAScript, with a yearly release cadence that has added modules, async/await, optional chaining, and more since ES2015 ended the long ES5 stagnation. Its concurrency model is an event loop plus a callback/microtask queue: nothing blocks, and async work resolves through promises. Prototypal inheritance underlies the `class` syntax added in ES2015, and closures make functions first-class citizens that capture their defining scope. It runs everywhere—browsers via V8, SpiderMonkey and JavaScriptCore, servers via Node.js, Deno and Bun, and edge runtimes via V8 isolates. TypeScript is a superset that adds static types and compiles away to plain JavaScript.