ts-node-starter-example

In a new folder, enter and accept all the defaults:

  npm init
  
Let us install the development dependencies:

  npm install -D typescript
  npm install -D tslint
  npm install -D nodemon
  
In this simple example, we will implement a simple Express application; so we install the dependencies:

  npm install express
  npm install @types/express
  
We create the TypeScript configuration; based on the TypeScript Node Starter project (explained there).

or 

  npx tsc --init --rootDir src --outDir lib --esModuleInterop --resolveJsonModule --lib es6,dom

tsconfig.json


```
{
    "compilerOptions": {
        "module": "commonjs",
        "esModuleInterop": true,
        "target": "es6",
        "noImplicitAny": true,
        "moduleResolution": "node",
        "sourceMap": true,
        "outDir": "dist",
        "baseUrl": ".",
        "paths": {
            "*": [
                "node_modules/*",
                "src/types/*"
            ]
        },
        "lib": [
            "es2015"
        ]
    },
    "include": [
        "src/**/*"
    ]
}
```

Observations:

The lib entry is not in the TypeScript Node Starter version
The code in this article runs without adding it
Went ahead and added it because I immediately had issues using configuration without it on other projects (including the GraphQL project)
The lib configuration is List of library files to be included in the compilation; Adding es2015, then allows TypeScript to fully support ES2015. I assumed it already did.
We create the TSLint configuration using the command:

  ./node_modules/.bin/tslint --init

and we add the three rules, interface-name, no-console, and quotemark (self-explanatory).

tslint.json

```

{
    "defaultSeverity": "error",
    "extends": [
        "tslint:recommended"
    ],
    "jsRules": {},
    "rules": {
        "interface-name": [false],
        "no-console": [false],
        "quotemark": [true, "single"]
    },
    "rulesDirectory": []
}
```


We update the main and scripts sections of package.json:

package.json

```
{
  "name": "hello-nodejs-typescript",
  "version": "1.0.0",
  "description": "",
  "main": "dist/server.js",
  "scripts": {
    "build-ts": "tsc",
    "start": "npm run serve",
    "serve": "node dist/server.js",
    "watch-node": "nodemon dist/server.js",
    "watch-ts": "tsc -w"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "nodemon": "^1.18.3",
    "tslint": "^5.11.0",
    "typescript": "^3.0.1"
  },
  "dependencies": {
    "@types/express": "^4.16.0",
    "express": "^4.16.3"
  }
}
```

Observations:

During development, we use both npm run watch-ts (recompiles application on source changes) and npm run watch-node (restarts application on recompilation)
npm run build-ts only compiles the application
npm run serve (npm run start) only starts the application
With this in place we can create our Hello World Express application; the only change is we use import instead of require.

src / server.ts


To develop, we run:

npm run watch-ts
and in a separate terminal we run:

npm run watch-node
and then opening the url http://localhost:3000/ in a browser we can see the output of the application.

If we update the server.js source, the application is recompiled and restarted; reloading the browser will reflect the change.