How to watch and compile all TypeScript sources?

you can watch all files like this

tsc *.ts --watch

The other answers may have been useful years ago, but they are now out of date.

Given that a project has a tsconfig file, run this command...

tsc --watch

... to watch for changed files and compile as needed. The documentation explains:

Run the compiler in watch mode. Watch input files and trigger recompilation on changes. The implementation of watching files and directories can be configured using environment variable. See configuring watch for more details.

To answer the original question, recursive directory watching is possible even on platforms that don't have native support, as explained by the Configuring Watch docs:

The watching of directory on platforms that don’t support recursive directory watching natively in node, is supported through recursively creating directory watcher for the child directories using different options selected by TSC_WATCHDIRECTORY

Create a file named tsconfig.json in your project root and include following lines in it:

{
    "compilerOptions": {
        "emitDecoratorMetadata": true,
        "module": "commonjs",
        "target": "ES5",
        "outDir": "ts-built",
        "rootDir": "src"
    }
}

Please note that outDir should be the path of the directory to receive compiled JS files, and rootDir should be the path of the directory containing your source (.ts) files.

Open a terminal and run tsc -w, it'll compile any .ts file in src directory into .js and store them in ts-built directory.

TypeScript 1.5 beta has introduced support for a configuration file called tsconfig.json. In that file you can configure the compiler, define code formatting rules and more importantly for you, provide it with information about the TS files in your project.

Once correctly configured, you can simply run the tsc command and have it compile all the TypeScript code in your project.

If you want to have it watch the files for changes then you can simply add --watch to the tsc command.

Here's an example tsconfig.json file

{
"compilerOptions": {
    "target": "es5",
    "module": "commonjs",
    "declaration": false,
    "noImplicitAny": false,
    "removeComments": true,
    "noLib": false
},
"include": [
    "**/*"
],
"exclude": [
    "node_modules",
    "**/*.spec.ts"
]}

In the example above, I include all .ts files in my project (recursively). Note that you can also exclude files using an "exclude" property with an array.

For more information, refer to the documentation: http://www.typescriptlang.org/docs/handbook/tsconfig-json.html