TypeScript Compiler Configuration

TypeScript compiler uses tsconfig.json to get configuration options for generating JavaScript code from TypeScript source-code. When you uses '$ tsc' command to compile TypeScript code, compiler searches for configurations located in tsconfig.json.

1. The tsconfig.json is generally put in the root folder of the project.
2. It provides the compiler options required to compile the project.

1. Creating tsconfig.json

Before we start using TypeScript, make sure we have installed it. To use conveniently, install it as global dependency so that we can use tsc command from console window.

Then use 'tsc --init' command to create tsconfig.json file in your project’s root folder.

$ npm install typescript -g 	//Install typescript

$ cd project_root		//Go to project's root folder

$ tsc --init			//Create tsconfig.json in project's root folder

A default tsconfig.json will be created.

{ 
   "compilerOptions":{ 
      "target":"es6",
      "moduleResolution":"node",
      "module":"commonjs",
      "declaration":false,
      "noLib":false,
      "emitDecoratorMetadata":true,
      "experimentalDecorators":true,
      "sourceMap":true,
      "pretty":true,
      "allowUnreachableCode":true,
      "allowUnusedLabels":true,
      "noImplicitAny":true,
      "noImplicitReturns":false,
      "noImplicitUseStrict":false,
      "outDir":"dist/",
      "baseUrl":"src/",
      "listFiles":false,
      "noEmitHelpers":true
   },
   "include":[ 
      "src/**/*"
   ],
   "exclude":[ 
      "node_modules"
   ],
   "compileOnSave":false
}

2. TypeScript Compiler Options

Let’s go through some important compiler options, we must know.

Option	Description
allowJs	Allow JavaScript files to be compiled. Default value is false.
alwaysStrict	Parse in strict mode and emit “use strict” for each source file. Default value is false.
module	The output module type e.g. “CommonJS”, “AMD“, “System“, “ES6“, “ES2015” or “ESNext“. Default value is CommonJS if target attribute is ES3 or ES5; else default is ES6.
target	Specify ECMAScript target version. Default value is ES3.
moduleResolution	Determine how modules get resolved. For module type ES6, AMD or System – default value is classic; else Node.
sourceMap	Indicates to generate sourcemap or not. Sourcemaps helps in debugging.
outDir	The location in which the transpiled files should be kept.
baseUrl or paths	Instructing TypeScript where it can find the type files.
watch	Used for livereload. It means that whenever any of the source file is changed, then the compiling process is re-triggered to generate the transpiled files again.
experimentalDecorators	This option enables using decorators in TypeScript projects. ES has not yet introduced decorators, so they are disabled by default.

Follow official page for complete list of compiler options.

3. Include and exclude options

These options takes an array of global patterns that need to be included in the compilation path, to add or remove files from compilation process.

"include":[ 
  "src/**/*",
  "src/app/shared/**/*",
  "typings/*.d.ts"
],
"exclude":[ 
  	"node_modules",
	 "jspm_packages",
	 "application", 
	 "system",
	 "dist"
]

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Happy Learning !!