What is the purpose of using tsconfig.json file ?

tsconfig.json file allows you to point the root level files and different compiler options to setup that require to compile a TypeScript based projects. The existence of this file in a project specifies that the given directory is the TypeScript project folder root.

Here is an example tsconfig.json file.

{
"compileOnSave": true,
"compilerOptions": {
        "target": "es5",
		"module": "system",
		"moduleResolution": "node",
		"noImplicitAny": true,
		"sourceMap": true,
        "removeComments": false
},
	"files": [
		"program.ts",
		"sys.ts"
	],
	"include": [
		"src/**/*"
	],
	"exclude": [
		"node_modules",
		"src/**/*.spec.ts"
	]
}

Lets understand what each option specifies:

• compileOnSave: If sets true, it instructs the IDE to automatically compile the given TypeScript files and generate the output.
• compilerOptions: It allows specifying additional options to the TypeScript compiler:
  • target: the language used for the compiled output, e.g. es5, es6.
  • module: the module manager used in the compiled output. system is for SystemJS, commonjs for CommonJS.
  • moduleResolution: the strategy used to resolve module declaration files (.d.ts files). With the node approach, they are loaded from the node_modules folder like a module (require('module-name'))
  • noImplicitAny: if sets false, Raise error on expressions and declarations with an implied any type.
  • sourceMap: if sets true, it will generate source map files to debug directly your application TypeScript files in the browser,
  • removeComments: if set, Remove all comments except copy-right header comments beginning with /*!
• files: Gives a list of TypeScript files that will be included by the compiler. The URL of the files can be both relative or absolute.
• include: Allows you to include a list of TypeScript files using the glob wildcards pattern.
• exclude: Allows you to exclude a list of TypeScript files using the glob wildcards pattern.