Modules, Runtime & Tooling

tsconfig & Module Resolution

tsconfig.json controls how TypeScript checks and emits a project: target, module system, strictness, JSX, included files, path aliases, library types, and resolution rules.

target controls emitted JavaScript syntax
module controls emitted module format
moduleResolution controls how imports are found
lib controls available ambient types
Strictness is part of architecture

App-oriented tsconfig shape

{
  "compilerOptions": {
    "target": "ES2022",
    "module": "ESNext",
    "moduleResolution": "Bundler",
    "lib": ["ES2022", "DOM", "DOM.Iterable"],
    "strict": true,
    "noUncheckedIndexedAccess": true,
    "exactOptionalPropertyTypes": true
  },
  "include": ["src"]
}

The right settings depend on runtime, bundler, and project type.

Important tsconfig options
Option	Controls	Common mistake
target	Output syntax	Assuming it polyfills APIs
module	Output module format	Mismatch with runtime
moduleResolution	How imports resolve	Using old mode with modern exports
lib	Available ambient types	Typing APIs not present in runtime
strict	Type-checking baseline	Leaving it off indefinitely
paths	Compile-time aliases	Forgetting runtime/bundler support