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Use strongly typed environment variables like a boss
JavaScript
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README.md

Usage

Use strongly typed environment variables like a boss:

npm install var

Then create a file named env.json in your root folder, or if you want a different path for your configuration file, you can set it via the ENV_VAR_CONFIG_FILE environment variable.

Your configuration contains default values and simple validation rules for your environment variables. Any environment variables defined prior to reading env.json will take precedence, but will be converted and validated according to the corresponding type defined in env.json.

Finally, just require the package, assign it to a variable and use that instead of process.env:

var env = require('var');

Any variables that aren't defined in process.env will receive the raw, unparsed value from env.json. This allows you, among other things, to set node-specific variables like NODE_ENV (useful in Express) or TZ from env.json.

Warning: process.env can only hold string values. That's the main reason this package exists.

Warning: some Node hosting providers don't support using spaces in environment variables through their web interface. You are free to use spaces in env.json though.

Supported types

  • string
  • number
  • boolean
  • date
  • object (including arrays)
  • function

Configuration

Strings

You should define default values for Node environment variables first in case you want to reference them later in your configuration:

{
  "NODE_ENV": "development",
  "TZ": "UTC",
  ...
}

Numbers

Just slap some numbers:

  "port": 3000

That was still a default value, just a shorthand for:

  "pageSize": {
    "default": 10
  }

Or if you want to be somewhat cryptic:

  "aspectRatio": {
    "type": "number",
    "default": "1.618"
  }

But you don't need to to that, floats are parsed just fine without the quotes and type specification.

What if you don't want a default value, just a strongly typed setting you can depend on:

  "limit": {
    "type": "number"
  }

Unless you set the required setting to true, the presence of the variable is optional.

Boolean

It's as simple as that:

  "gzip": true

But even if you set it to the string "false" in your server configuration, the type will still be inferred from the env.json settings, so env.gzip would evaluate to the boolean false, not to the string "false".

Dates

Just use anything that returns a valid date after being called with new Date():

  "minDate": {
    "type": "date",
    "default": "1899-12-31"
  }

Objects and Arrays

You can have complex object hierarchies in your configuration:

  "log": {
    "production": {
      "console": "error",
      "loggly": ["info", "error"],
      "mail": "alert"
    },
    "default": {
      "console": ["info", "error"],
      "loggly": ["info", "error"],
      "mail": ["error", "alert"]
    }
  }

Functions

Let's try something even more advanced:

  "maxSessionLength": {
    "type": "function",
    "default": "60 * 60 * 1000"
  }

Or why not be a bit more dynamic:

  "maxExtendedSessionLength": {
    "type": "function",
    "default": "30 * 24 * this.maxSessionLength"
  }

Yes, this refers to all environment variables that have already been parsed, so order is important.

Your function can contain anything, but bear in mind that the string is evaluated and immediately returned to save you some writing in the most common use cases. However, if you need to do some complex calculation, you still can by using an in-place function:

  "today": {
    "type": "function",
    "default": "(function () { var now = new Date(); return new Date(now.getFullYear(), now.getMonth(), now.getDate()) }())"
  },

Warning: Functions aren't strongly typed, so they can return values of different types.

Enviroments

But what about different environments:

  "sessionSecret": {
    "development": "not so secret",
    "required": true
  }

Your session encryption algorithm would fail if you didn't pass a valid value to it. This sets a default value in development, but throws an error if sessionSecret is not defined in other environments.

You can use anything as an environment name, except type, default and required:

  "logLevel": {
    "development": 3,
    "test": 2,
    "staging": 1,
    "production": 1,
    "default": 0
  }

License

Copyright (c) 2013 Vladimir Sabev

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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