tsc-watch

The nodemon for TypeScript

tsc-watch starts the installed TypeScript compiler (tsc) with --watch parameter, with the ability to react to compilation status. tsc-watch was created to allow an easy dev process with TypeScript. Commonly used to restart a node server, similar to nodemon but for TypeScript.

Anything that you can do with tsc you can do with tsc-watch, the only difference is that tsc-watch can react to compilation status.

Argument	Description
--onSuccess COMMAND	Executes COMMAND on every successful compilation.
--onFirstSuccess COMMAND	Executes COMMAND on the first successful compilation.
--onEmit COMMAND	Executes debounced COMMAND on every emitted file, ignoring unchanged files and disregards compilation success or failure.
--onEmitDebounceMs DELAY	Delay by which to debounce --onEmit (default: 300).
--onFailure COMMAND	Executes COMMAND on every failed compilation.
--onCompilationStarted COMMAND	Executes COMMAND on every compilation start event (initial and incremental).
--onCompilationComplete COMMAND	Executes COMMAND on every successful or failed compilation.
--maxNodeMem	Calls node with a specific memory limit max_old_space_size, to use if your project needs more memory.
--noColors	By default tsc-watch adds colors the output with green on success, and in red on failure. Add this argument to prevent that.
--noClear	In watch mode the tsc compiler clears the screen before reporting Add this argument to prevent that.
--signalEmittedFiles	Will run tsc compiler with --listEmittedFiles, but hiding TSFILE lines. Use it to enable file_emitted event, while keeping tsc stdout silent.
--silent	Do not print any messages on stdout.
--compiler PATH	The PATH will be used instead of typescript compiler. Default is typescript/bin/tsc

Notes:

• That all the above COMMANDs will be killed on process exit. (Using SIGTERM)

• A COMMAND is a single command and not multi command like script1.sh && script2.sh

• Any child process (COMMAND) will be terminated before creating a new one.

Install

npm install tsc-watch --save-dev

## for command-line usage
npm install -g typescript tsc-watch

Usage

From Command-Line

## Watching a project (with tsconfig.json)
tsc-watch --onSuccess "node ./dist/server.js"

## Beep on failure
tsc-watch --onFailure "echo Beep! Compilation Failed"

## Watching a single file
tsc-watch server.ts --outDir ./dist --onSuccess "node ./dist/server.js"

## Custom compiler
tsc-watch --onSuccess "node ./dist/server.js" --compiler my-typescript/bin/tsc

From npm script

"dev-server": "tsc-watch --noClear -p ./src/tsconfig.json --onSuccess \"node ./dist/server.js\"",

From javascript

You can see a detailed example here

The client is implemented as an instance of Node.JS's EventEmitter, with the following events:

• started - Emitted upon the compilation start (initial or incremental).
• first_success - Emitted upon first successful compilation.
• subsequent_success - Emitted upon every subsequent successful compilation.
• compile_errors - Emitted upon every failing compilation.
• file_emitted - Emitted upon every file transpiled if --listEmittedFiles is used.

Once subscribed to the relevant events, start the client by running watch.start()

To kill the client, run watch.kill()

Example usage:

// Using CommonJS:
const { TscWatchClient } = require('tsc-watch/client');
// Using ES6 import:
import { TscWatchClient } from 'tsc-watch/client';

const watch = new TscWatchClient();

watch.on('started', () => {
  console.log('Compilation started');
});

watch.on('first_success', () => {
  console.log('First success!');
});

watch.on('success', () => {
  // Your code goes here...
});

watch.on('compile_errors', () => {
  // Your code goes here...
});

watch.start('--project', '.');

try {
  // do something...
} catch (e) {
  watch.kill(); // Fatal error, kill the compiler instance.
}

Notes:

• The (onSuccess) COMMAND will not run if the compilation failed.
• The (onEmit) COMMAND will not run if the compilation succeeded with no changed files, unless it is the first success.
• The (onEmit) COMMAND will run even if the compilation failed, but emitted changed files.
• The (onEmit) COMMAND will not run 100 times for 100 files, due to --onEmitDebounce
• The (onEmit) COMMAND is not cancelling the onSuccess/onFirstSuccess/onFailure/onCompilationComplete/onCompilationStarted commands and vice versa.
• tsc-watch is using the currently installed TypeScript compiler.
• tsc-watch is not changing the compiler, just adds the new arguments, compilation is the same, and all other arguments are the same.