finished implementation, working on local machine

Author: williexu

index.js

@@ -1,13 +1,44 @@
-var http = require('http');
+const express = require('express');
+const async = require('async');
+const msRestAzure = require('ms-rest-azure');
+const KeyVault = require('azure-keyvault');
+const KeyVaultManagementClient = require('azure-arm-keyvault')
+const KEY_VAULT_URI = "https://wilxkv.vault.azure.net/";
 
-var server = http.createServer(function(request, response) {
+let app = express();
+let clientId = process.env['CLIENT_ID']; // service principal
+let domain = process.env['DOMAIN']; // tenant id
+let secret = process.env['APPLICATION_SECRET'];
 
-    response.writeHead(200, {"Content-Type": "text/plain"});
-    response.end("Hello World!");
+function get_key_vault_credentials(){
+  if (process.env.APPSETTING_WEBSITE_SITE_NAME){
+    return msRestAzure.loginWithAppServiceMSI();
+  } else {
+    return msRestAzure.loginWithServicePrincipalSecret(clientId, secret, domain);
+  }
+} 
 
+function get_key_vault_secret(credentials) {
+  let keyVaultClient = new KeyVault.KeyVaultClient(credentials);
+  return keyVaultClient.getSecret(KEY_VAULT_URI, 'secret', "");
+}
+
+app.get('/', function (req, res) {
+  get_key_vault_credentials().then(
+    get_key_vault_secret
+  ).then(function (secret){
+    res.send(`Your secret value is: ${secret.value}.`);
+  }).catch(function (err) {
+    res.send(err);
+  });
+});
+
+app.get('/ping', function (req, res) {
+  res.send('Hello World!!!');
 });
 
-var port = process.env.PORT || 1337;
-server.listen(port);
+let port = process.env.PORT || 3000;
 
-console.log("Server running at http://localhost:%d", port);
+app.listen(port, function () {
+  console.log(`Server running at http://localhost:${port}`);
+});