TSC

tsc is the TypeScript compiler, a command-line tool that compiles TypeScript code into JavaScript. It is part of the TypeScript language project maintained by Microsoft. TypeScript is a typed superset of JavaScript that adds optional static types and other features. When tsc processes .ts and .tsx files, it performs type checking (when enabled) and emits JavaScript according to the configured output settings.

The compiler is distributed via npm as the typescript package. Developers install it in their project or globally and run tsc to perform compilation. A project can be configured with a tsconfig.json file, which specifies compiler options, file inclusions, exclusions, and references. tsc can run in watch mode (-w) to recompile on changes, and supports incremental compilation for faster builds. It can emit declaration files (.d.ts) to provide type information to consumers of a library.

Key options include target (es5, es2015, es2016, etc.), module (commonjs, esnext), lib, strict, noImplicitAny, skipLibCheck, outDir, rootDir, baseUrl, paths, etc. It can resolve module imports, handle JSX in .tsx files, and support interop with non-TypeScript code. It also supports project references to build multi-package workspaces.

Typical usage: install TypeScript (npm i -D typescript), run npx tsc --init to create tsconfig.json, then run npx tsc to compile. Use tsc -w or tsc --watch for automatic recompilation. The output is JavaScript files in the configured directory along with optional source maps.