Last Updated: February 25, 2016
· adam boczek

Using Node.js with Express as a Simple API Mock Server

This code snippet allows you to use Node.js with Express as a simple API mock server.
This idea I have found in one of the projects I was involved in. The author is unknown but nevertheless many thanks to him/her!

The code below creates a server with an API that is based on the file structure, means:

will be mapped to http://ipaddress:port/api/customers

will be mapped to http://ipaddress:port/api/customers/1

and so on...

If you need a new one e.g. "http://ipaddress:port/api/orders" just create a new file "orders.json" in the required directory "/test/mocks/api/", deploy it and restart the server.

It is very useful if just started to create your API and want to test some GETs, see "how it feels".

I use it locally but also on OpenShift. It works perfectly.

/* Define some initial variables. */
var applicationRoot = __dirname.replace(/\\/g,"/"),
  ipaddress = process.env.OPENSHIFT_NODEJS_IP || '',
  port = process.env.OPENSHIFT_NODEJS_PORT || 8080;
  mockRoot = applicationRoot + '/test/mocks/api',
  mockFilePattern = '.json',
  mockRootPattern = mockRoot + '/**/*' + mockFilePattern,
  apiRoot = '/api',
  fs = require("fs"),
  glob = require("glob");

/* Create Express application */
var express = require("express");
var app = express();

/* Configure a simple logger and an error handler. */
app.configure(function() {
  app.use(express.errorHandler({ dumpExceptions: true, showStack: true }));

/* Read the directory tree according to the pattern specified above. */
var files = glob.sync(mockRootPattern);

/* Register mappings for each file found in the directory tree. */
if(files && files.length > 0) {
  files.forEach(function(fileName) {

    var mapping = apiRoot + fileName.replace(mockRoot, '').replace(mockFilePattern,'');

    app.get(mapping, function (req, res) {
      var data =  fs.readFileSync(fileName, 'utf8');
      res.writeHead(200, { 'Content-Type': 'application/json' });

    console.log('Registered mapping: %s -> %s', mapping, fileName);
} else {
    console.log('No mappings found! Please check the configuration.');

/* Start the API mock server. */
console.log('Application root directory: [' + applicationRoot +']');
console.log('Mock Api Server listening: [http://' + ipaddress + ':' + port + ']');
app.listen(port, ipaddress);