Ajax proxy

A proxy server for redirecting HTTP requests from client-side code using credentials stored on the back end.

Based on Expressjs and http-proxy-middleware.

Configuration instructions include steps for deploying to Heroku, but proxy can be deployed to any Node environment.

Configuration

1. Clone this repo to your local machine.
2. Create a new app on Heroku.
3. Store your API credentials using config vars.

• On the Heroku dashboard for your app, click Settings, then click Reveal Config Vars.
• Enter a name for the config var, paste your API key or other credential as the value, then click Add.

4. Customize index.js for your endpoint:

• In the filter function, specify your app's front end origin as the value for req.headers.origin.

  // replace www.myapp.example with origin(s) that your content will be served from
  return (req.headers.origin === 'https://www.myapp.example');
  // multiple origin version:
  // return ((req.headers.origin === 'http://myapp.example') ||
  //         (req.headers.origin === 'https://www.myapp.example'));

• In the apiOptions object, specify the URL of the web service you're connecting to as the value for target.

  var apiOptions = {
    // replace api.datasource.example with the url of your target host
    target: 'https://api.datasource.example',
    ...
    };

• In the apiOptions object, update onProxyReq to use the keyname provided by your target host and the name of the config var you created in Heroku to store your credential value.

  var apiOptions = {
    ...
    onProxyReq: (proxyReq) => {
      // append key-value pair for API key to end of path
      // using KEYNAME provided by web service
      // and KEYVALUE stored in Heroku config var
      proxyReq.path += ('&KEYNAME=' + process.env.KEYVALUE);
    },
    logLevel: 'debug' // verbose server logging
  }; 

5. In your browser, return to your Heroku Dashboard, click Deploy, then follow the steps to deploy your customized code from your local machine to Heroku.

6. In the front-end code for your app, rewrite the URL in your ajax request to use your Heroku proxy app as the base URL.

Example

The following code uses the U.S. National Park Service API.

var express = require('express');
var proxy = require('http-proxy-middleware');

var filter = function (pathname, req) {
  return ((req.headers.origin === 'http://127.0.0.1:5500') ||
          (req.headers.origin === 'https://127.0.0.1:5500'));
};

var npsOptions = {
  target: 'https://developer.nps.gov', 
  changeOrigin: true, 
  pathRewrite: {
    '^/nps/': '/', 
  },
  onProxyReq: (proxyReq, req, res) => {
    proxyReq.path += ('&api_key=' + process.env.NPS_APIKEY);
  },
  logLevel: 'debug'
};

var npsProxy = proxy(filter, npsOptions);

var app = express();
app.set('port', (process.env.PORT || 5000));

app.use('/nps', npsProxy);

app.listen(app.get('port'));

Starting with a front-end request like

https://<HEROKU-INSTANCE>.herokuapp.com/nps/api/v1/parks?stateCode=ca

the proxy rewrites and forwards the request as

https://developer.nps.gov/api/v1/parks?stateCode=ca&api_key=########

(where ######## is the secret key stored in the Heroku Config Var with the name NPS_APIKEY)

License

The MIT License (MIT)

Copyright (c) 2019 Sasha Vodnik