add typescript example (#362)

README.md

@@ -255,7 +255,7 @@ errorReporter.client.report(new Error('faq example'))
 `client` will not be configured correctly because it was constructed before `dotenv.config()` was executed. There are (at least) 3 ways to make this work.
 
 1. Preload dotenv: `node --require dotenv/config index.js` (_Note: you do not need to `import` dotenv with this approach_)
-2. Import `dotenv/config` instead of `dotenv` (_Note: you do not need to call `dotenv.config()` and must pass options via the command line with this approach_)
+2. Import `dotenv/config` instead of `dotenv` (_Note: you do not need to call `dotenv.config()` and must pass options via the command line or environment variables with this approach_)
 3. Create a separate file that will execute `config` first as outlined in [this comment on #133](https://github.com/motdotla/dotenv/issues/133#issuecomment-255298822)
 
 ## Contributing Guide

examples/typescript/.env.example

@@ -0,0 +1,3 @@
+NODE_ENV=example
+SAMPLE_KEY=defined
+ERR_API_KEY=qwerty12345

examples/typescript/.gitignore

@@ -0,0 +1 @@
+dist/

examples/typescript/README.md

@@ -0,0 +1,16 @@
+# TypeScript Example
+
+> Use `dotenv` in a simple TypeScript project.
+
+`src/lib/errors.ts` requires an environment variable at time of export so `src/lib/env.ts` contains `dotenv` configuration and is imported first in `src/index.ts`.
+
+1. `npm install`
+2. `npm run build`
+3. `npm start`
+
+Expected output:
+
+```
+Current NODE_ENV is example
+Sample key is defined
+```

examples/typescript/package.json

@@ -0,0 +1,13 @@
+{
+  "scripts": {
+    "build": "tsc",
+    "start": "node dist/index.js"
+  },
+  "dependencies": {
+    "dotenv": "latest"
+  },
+  "devDependencies": {
+    "@types/dotenv": "^6.1.0",
+    "typescript": "^3.2.2"
+  }
+}

examples/typescript/src/index.ts

@@ -0,0 +1,8 @@
+import "./lib/env"
+import errorReporter from "./lib/errors"
+
+console.log(`Current NODE_ENV is ${process.env.NODE_ENV}`)
+
+console.log(`Sample key is ${process.env.SAMPLE_KEY}`)
+
+errorReporter.report(new Error("example"))

examples/typescript/src/lib/env.ts

@@ -0,0 +1,5 @@
+import { resolve } from "path"
+
+import { config } from "dotenv"
+
+config({ path: resolve(__dirname, "../../.env.example") })

examples/typescript/src/lib/errors.ts

@@ -0,0 +1,17 @@
+class ErrorReporter {
+  private apiKey: string
+
+  constructor(apiKey: string) {
+    if (apiKey === undefined || apiKey === "") {
+      throw new Error("apiKey required")
+    }
+
+    this.apiKey = apiKey
+  }
+
+  report(err: Error) {
+    // could use apiKey here to send error somewhere
+  }
+}
+
+export default new ErrorReporter(process.env.ERR_API_KEY)

examples/typescript/tsconfig.json

@@ -0,0 +1,21 @@
+{
+  "compilerOptions": {
+    "module": "commonjs",
+    "esModuleInterop": true,
+    "target": "es6",
+    "noImplicitAny": true,
+    "moduleResolution": "node",
+    "sourceMap": true,
+    "outDir": "dist",
+    "baseUrl": ".",
+    "paths": {
+      "*": [
+        "node_modules/*",
+        "src/types/*"
+      ]
+    }
+  },
+  "include": [
+    "src/**/*"
+  ]
+}