CheatTypeScript compiler (tsc) Typed JS compiler
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Start here
tsc --initCreate a tsconfig.json
tscCompile the project
tsc --noEmitType-check only
tsc --watchRecompile on change
tsc -p <path>
Use a specific config
tsc --showConfig
Print the resolved config
tsc --buildBuild project references
tsc --ignoreConfig <file>
Compile files, skip config
Concepts
- tsconfig.json options + files
- Type check errors, exit code 1
- JavaScript outDir
Project setup
tsc --initCreate a tsconfig.json
Refuses if one already exists in the directory.
tscCompile using the nearest tsconfig.json
tsc -p <path>
Compile a config file or directory
Also written --project.
tsc --noEmitType-check without writing files
tsc --watchRecompile when files change
Add --preserveWatchOutput to keep earlier output on screen.
tsc --ignoreConfig <file>
Compile given files, ignore tsconfig
tsc --versionShow the compiler version
tsc --help --all
List every compiler option
tsc --locale <code>
Messages in another language
tsconfig keys
"extends": "<file>"
Inherit another config
"include": ["src"]
Files to compile
"exclude": ["dist"]
Files to skip
"files": ["a.ts"]
Explicit file list
"references": [{"path":
"<dir>"}]
Link another project
"compilerOptions": {}
Where all options below go
Language & modules
--target esnextSyntax level of emitted JS
Default is es2025 in 7; es5 is no longer allowed.
--module nodenext
Module format for Node projects
--module preserve
Keep imports as written (bundlers)
--moduleResolution bundler
Resolution for bundler setups
--lib <list>
Built-in type libraries to include
Add dom for browser code, e.g. --lib esnext,dom.
--types <list>
Which @types packages to load
An empty list loads none; add node explicitly.
--jsx react-jsxHow JSX is compiled
--resolveJsonModule
Allow importing .json files
--allowJsInclude .js files in the project
--checkJsReport errors in .js files
--moduleDetection force
Treat every file as a module
--allowImportingTsExtensions
Allow imports ending in .ts
Needs --noEmit or --emitDeclarationOnly.
--rewriteRelativeImportExtensions
Rewrite .ts imports to .js on emit
--rootDirs <list>
Merge directories for resolution
"paths": {"@/*": ["./src/*"]}
Alias import prefixes
Only affects type checking; the runtime or bundler must
resolve aliases too.
Type checking
--strictEnable all strict checks
On by default in 7; set false to opt out.
--noUncheckedIndexedAccess
Indexed access may be undefined
--exactOptionalPropertyTypes
Optional means absent, not undefined
--noImplicitReturns
Every code path must return
--noImplicitOverride
Require override on subclass methods
--noUnusedLocals
Error on unused variables
--noUnusedParameters
Error on unused parameters
--noFallthroughCasesInSwitch
Error on switch fallthrough
--noPropertyAccessFromIndexSignature
Force obj["key"] on index types
--skipLibCheckSkip checking .d.ts files
Speeds up checks and hides errors inside dependencies.
--noCheckSkip type checking, still emit
Emit
--outDir <dir>
Write output files here
--rootDir <dir>
Root of the input tree
Decides how outDir mirrors the source layout.
--declarationEmit .d.ts files
--emitDeclarationOnly
Emit only .d.ts files
--sourceMapEmit .js.map files
--declarationMap
Emit .d.ts.map files
--noEmitOnErrorEmit nothing if there are errors
--outFile <file>
Bundle all output into one file
--removeComments
Strip comments from output
--verbatimModuleSyntax
Keep imports/exports as written
Requires import type for type-only imports.
--isolatedModules
Require per-file safe code
--esModuleInterop
Smoother CommonJS default imports
On by default in 7.
--erasableSyntaxOnly
Forbid enums and namespaces
Keeps code compatible with Node type stripping.
Projects & builds
tsc --buildBuild projects whose inputs changed
Short form -b; follows references.
tsc -b --watchRebuild referenced projects on change
tsc -b --cleanDelete build outputs
tsc -b --forceRebuild even if up to date
tsc -b --dryShow what would be built
tsc -b --verbose
Explain why projects rebuild
--compositeMake the project referenceable
Implies declaration and incremental.
--incrementalCache state in .tsbuildinfo
--tsBuildInfoFile <file>
Where the incremental cache lives
Debugging
tsc --showConfig
Print the final merged config
Shows what extends and defaults resolve to.
tsc --listFilesList every file in the program
tsc --listFilesOnly
List files and stop
tsc --explainFiles
Why each file was included
tsc --traceResolution
Log module lookup steps
Pipe through grep for one specifier.
tsc --listEmittedFiles
Print files written
tsc --diagnostics
Show timing and memory use
tsc --extendedDiagnostics
More detailed performance stats
tsc --generateTrace <dir>
Write a performance trace
tsc --pretty false
Plain one-line errors
Better for CI logs and grep.
Recipes
{ "compilerOptions": { "module": "nodenext", "target": "esnext", "outDir": "dist", "types": ["node"], "skipLibCheck": true }, "include": ["src"]}# package.json scripts"typecheck": "tsc --noEmit","build": "tsc"tsc --explainFiles | grep -A3 <name>tsc --traceResolution | grep <module># root tsconfig.json{ "files": [], "references": [ {"path": "packages/core"}, {"path": "packages/app"} ] }tsc -b
