Added sample for Using Environment Variables.

.gitignore

@@ -10,3 +10,4 @@ logs/
 .nyc_output
 yarn.lock
 package-lock.json
+.DS_Store

functions/env_vars/README.md

@@ -0,0 +1,27 @@
+<img src="https://avatars2.githubusercontent.com/u/2810941?v=3&s=96" alt="Google Cloud Platform logo" title="Google Cloud Platform" align="right" height="96" width="96"/>
+
+# Google Cloud Functions - Using Environment Variables sample
+
+See:
+
+* [Cloud Functions Using Environment Variables tutorial][tutorial]
+* [Cloud Functions Using Environment Variables sample source code][code]
+
+[tutorial]: https://cloud.google.com/functions/docs/env-var
+[code]: index.js
+
+## Deploy and run the sample
+
+See the [Cloud Functions Using Environment Variables tutorial][tutorial].
+
+## Run the tests
+
+1. Read and follow the [prerequisites](../../#how-to-run-the-tests).
+
+2. Install dependencies:
+
+        npm install
+
+3. Run the tests:
+
+        npm test

functions/env_vars/index.js

@@ -0,0 +1,23 @@
+/**
+ * Copyright 2016, Google, LLC.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+'use strict';
+
+// [START functions_env_vars]
+exports.envVar = (req, res) => {
+  // Sends 'bar' as response
+  res.send(process.env.FOO);
+};
+// [END functions_env_vars]

functions/env_vars/package.json

@@ -0,0 +1,30 @@
+{
+  "name": "nodejs-docs-samples-env-vars",
+  "version": "0.0.1",
+  "private": true,
+  "license": "Apache-2.0",
+  "author": "Google Inc.",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/GoogleCloudPlatform/nodejs-docs-samples.git"
+  },
+  "engines": {
+    "node": ">=4.3.2"
+  },
+  "scripts": {
+    "lint": "repo-tools lint",
+    "pretest": "npm run lint",
+    "test": "ava -T 20s --verbose test/*.test.js"
+  },
+  "dependencies": {},
+  "devDependencies": {
+    "@google-cloud/nodejs-repo-tools": "2.2.1",
+    "ava": "0.25.0",
+    "semistandard": "^12.0.1",
+    "sinon": "4.4.2"
+  },
+  "cloud-repo-tools": {
+    "requiresKeyFile": true,
+    "requiresProjectId": true
+  }
+}

functions/env_vars/test/index.test.js

@@ -0,0 +1,41 @@
+/**
+ * Copyright 2016, Google, LLC.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+'use strict';
+
+const sinon = require(`sinon`);
+const test = require(`ava`);
+const functions = require(`../`);
+
+function getMocks () {
+  const req = {};
+  const res = {
+    send: sinon.stub().returnsThis()
+  };
+
+  return {
+    req: req,
+    res: res
+  };
+}
+
+test.serial(`should read env vars`, (t) => {
+  const mocks = getMocks();
+  process.env['FOO'] = 'bar';
+
+  functions.envVar(mocks.req, mocks.res);
+
+  t.true(mocks.res.send.calledWith('bar'));
+});