Usefull tool to create a json configuration file for your js apps.

Motivation

We can easily use environment variables for app configuration. But when you want more complex configuration structure, probably a .env file will not solve your problem. Env files needs to prefix every key, like this sample:

GOOGLE_MAPS_URL:...
GOOGLE_MAPS_KEY:...

Probably you want to use some more structured like:

{
    "GOOGLE_MAPS": {
        "URL": "...",
        "KEY": "..."
    }
}

And you can do it. But when you have a multiple environments (local, qa, staging, production), it comes to be more complicated.

You probably have one .env file for each environemnt and a lot of duplicated keys. For example:

// dev.env
GOOGLE_MAPS_KEY:my_google_maps_key
API_URL:http://localhost:3000/api

// qa.env
GOOGLE_MAPS_KEY:my_google_maps_key
API_URL:http://qa.mysite.com/api

Each of the environments have the same google maps api key. It could be easier...

RESUME IN ACTION

Shoot first, ask later.

Open the terminal in root of your project and execute npm install --save-dev app-json-env-gen

Create a folder named __env__ in the root.

Inside the __env__, create two files: global.env.js and qa.env.js.

Now your project must seems like:

+ root
|-+ __env__
  |-- global.env.js
  |-- qa.env.js
|-- packages.json
|-- ...other files

Inside the global.env.js, add:

module.exports = {
    meta: {},
    data: {
        GOOGLE_MAPS: {
            URL: 'https://googlemaps.fake.api',
            KEY: 'th1sisafak3key'
        },
        BACKEND_API: {
            URL: 'https://mysite.com/api'
        }
    }
}

Inside the qa.env.js, add:

module.exports = {
    meta: {
        from: 'global'
    },
    data: {
        BACKEND_API: {
            URL: 'https://qa.mysite.com/api'
        }
    }
}

Open your package.json and add this script:

"env-qa": "node ./node_modules/app-json-env-gen/cli.js target=qa output=./env.json"

In the terminal, run npm run env-qa

Your env file will be created in the env.json with:

{
    "GOOGLE_MAPS": {
        "URL": "https://googlemaps.fake.api",
        "KEY": "th1sisafak3key"
    },
    "BACKEND_API": {
        "URL": "https://qa.mysite.com/api"
    }
}

How it works

In fact, this lib is not more than a file merger with recursive parent strategy.

Config files folder

By default, this lib will use the __env__ folder for the enviroment config files.

If you want to use a custom folder, you can use the dir parameter:

"env-qa": "node ./node_modules/app-json-env-gen/cli.js dir=./my-envs target=qa output=./env.json"

Config file

When you create a config file, you create the file with this name: <target>.env.js.

In our sample, we created two targets: global and qa, but we can create what we want.

The file have this structure:

{
    "meta": {
        "from": "<other_target>"
    },
    "data": {}
}

This file is divided into two sections:

meta

This section contains some parameters for the generator.

Today, exist only one attribute named from. When this attribute is provided, the generator will copy the values from the source target and these values will be merged with this file.

So, in the example, we have created a global and a qa file. In the qa file, we add the from: "global" to the meta section.

When we did it, we told to the lib: get the data from the global.env.js file. I will override it with my own data.

So, it could be recursive. If we have this three files:

// global.env.js
module.exports = {
    meta: {},
    data: {
        name: 'global',
        version: 1
    }
}

// dev.env.js
module.exports = {
    meta: {
        from: 'global'
    },
    data: {
        name: 'dev',
        apiUrl: 'http://dev.site.com/api',
        debug: true
    }
}

// local.env.js
module.exports = {
    meta: {
        from: 'dev'
    },
    data: {
        name: 'local',
        apiUrl: 'http://localhost:3000/api'
    }
}

And we run the command node ./node_modules/app-json-env-gen/cli.js target=local output=./env.json

The result will be the merge of global > dev > local:

{
    "name": "local",
    "apiUrl": "http://localhost:3000/api",
    "version": 1,
    "debug": true
}

data

The data section is where you will put all the data that will be added to the resultant json file.

Command line

To execute the generator, we use the cli from node_modules in this format:

node ./node_modules/app-json-env-gen/cli.js dir=./my-envs target=qa output=./env.json

Where:

• node: invoking the command using nodejs.
• ./node_modules/app-json-env-gen/cli.js: the cli lib file that will be executed.
• dir=./my-envs: the directory that contains .env.js files, you can change the ./my-envs for your custom folder. This is optional, default __env__.
• target=qa: this is the target file used as a primary file. In this sample, is qa.env.js, if you change to target=potato it will use the potato.env.js as the main file.
• output=./env.json: this is the path that generated file will be created. You can change the ./env.json to the path you want.
  • If you use a .js extension, it will generate a js file with module.exports instead pure json.

Other options are available too:

Thanks to