tsconfig.json

Basic

It is extremely easy to get started with tsconfig.json as the basic file you need is:

{}

i.e. an empty JSON file at the root of your project. This way TypeScript will include all the .ts files in this directory (and sub directories) as a part of the compilation context. It will also select a few sane default compiler options.

compilerOptions

You can customize the compiler options using compilerOptions:

{
  "compilerOptions": {

    /* Basic Options */                       
    "target": "es5",                       /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', or 'ESNEXT'. */
    "module": "commonjs",                  /* Specify module code generation: 'commonjs', 'amd', 'system', 'umd' or 'es2015'. */
    "lib": [],                             /* Specify library files to be included in the compilation:  */
    "allowJs": true,                       /* Allow JavaScript files to be compiled. */
    "checkJs": true,                       /* Report errors in .js files. */
    "jsx": "preserve",                     /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
    "declaration": true,                   /* Generates corresponding '.d.ts' file. */
    "sourceMap": true,                     /* Generates corresponding '.map' file. */
    "outFile": "./",                       /* Concatenate and emit output to single file. */
    "outDir": "./",                        /* Redirect output structure to the directory. */
    "rootDir": "./",                       /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
    "removeComments": true,                /* Do not emit comments to output. */
    "noEmit": true,                        /* Do not emit outputs. */
    "importHelpers": true,                 /* Import emit helpers from 'tslib'. */
    "downlevelIteration": true,            /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
    "isolatedModules": true,               /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */

    /* Strict Type-Checking Options */        
    "strict": true,                        /* Enable all strict type-checking options. */
    "noImplicitAny": true,                 /* Raise error on expressions and declarations with an implied 'any' type. */
    "strictNullChecks": true,              /* Enable strict null checks. */
    "noImplicitThis": true,                /* Raise error on 'this' expressions with an implied 'any' type. */
    "alwaysStrict": true,                  /* Parse in strict mode and emit "use strict" for each source file. */

    /* Additional Checks */                   
    "noUnusedLocals": true,                /* Report errors on unused locals. */
    "noUnusedParameters": true,            /* Report errors on unused parameters. */
    "noImplicitReturns": true,             /* Report error when not all code paths in function return a value. */
    "noFallthroughCasesInSwitch": true,    /* Report errors for fallthrough cases in switch statement. */

    /* Module Resolution Options */           
    "moduleResolution": "node",            /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
    "baseUrl": "./",                       /* Base directory to resolve non-absolute module names. */
    "paths": {},                           /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
    "rootDirs": [],                        /* List of root folders whose combined content represents the structure of the project at runtime. */
    "typeRoots": [],                       /* List of folders to include type definitions from. */
    "types": [],                           /* Type declaration files to be included in compilation. */
    "allowSyntheticDefaultImports": true,  /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */

    /* Source Map Options */                  
    "sourceRoot": "./",                    /* Specify the location where debugger should locate TypeScript files instead of source locations. */
    "mapRoot": "./",                       /* Specify the location where debugger should locate map files instead of generated locations. */
    "inlineSourceMap": true,               /* Emit a single file with source maps instead of having a separate file. */
    "inlineSources": true,                 /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */

    /* Experimental Options */                
    "experimentalDecorators": true,        /* Enables experimental support for ES7 decorators. */
    "emitDecoratorMetadata": true          /* Enables experimental support for emitting type metadata for decorators. */
  }
}

These (and more) compiler options will be discussed later.

TypeScript compiler

Good IDEs come with built in support for on the fly ts to js compilation. However, if you want to run the TypeScript compiler manually from the command line when using tsconfig.json, you can do it in a few ways:

• Just run tsc and it will look for tsconfig.json in the current as well as all parent folders till it finds it.

• Run tsc -p ./path-to-project-directory. Of course the path can be absolute or relative to the current directory.

You can even start the TypeScript compiler in watch mode using tsc -w and it will watch your TypeScript project files for changes.