node.js deep dive: Passing config variables through jade

Using a MEAN stack knockoff, I needed to pass variables configured in the server environment, to make them accessible to client side javascript. In doing so I had to tangle with nconf and jade.

Here was my solution.

My config looks like this:

  NODE_ENV : development,
  ui_varables {
     var1: one,
     var2: two

First I had to make sure that the necessary config variables were being passed. MEAN uses the node nconf package, and by default is set up to limit which variables get passed from the environment. I had to remedy that:



  .env(['PORT', 'NODE_ENV', 'FORCE_DB_SYNC'] ) // Load only these environment variables
  store: {
    NODE_ENV: 'development'

after modifications:

  .env('__') // Load ALL environment variables
  // double-underscore replaces : as a way to denote hierarchy
  store: {
    NODE_ENV: 'development'

Now I can set my variables like this:

export ui_varables__var1=first-value
export ui_varables__var2=second-value

Note: I reset the “heirarchy indicator” to “__” (double underscore) because its default was “:”, which makes variables more difficult to set from bash.

Now the jade part:
Next the values need to be rendered, so that javascript can pick them up on the client side. A straightforward way to write these values to the index file. Because this is a one-page app (angular), this page is always loaded first. I think ideally this should be a javascript include file (just to keep things clean), but this is good for a demo.


'use strict';

* Module dependencies.
var _ = require('lodash');
var config = require('../../config/config');

exports.render = function(req, res) {
  res.render('index', {
    user: req.user ? JSON.stringify(req.user) : "null",
    //new lines follow:
    config_defaults : {
       ui_defaults: JSON.stringify(config.configwriter_ui).replace(/<\//g, '<\\/')  //NOTE: the replace is xss prevention


extends layouts/default

block content
    window.user = !{user};
    //new line here
    defaults = !{config_defaults.ui_defaults};

In my rendered html, this gives me a nice little script:

<script type="text/javascript">
 window.user = null;	 	 
 defaults = {"var1":"first-value","var2:"second-value"};

From this point it’s easy for angular to utilize the code.

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