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1.0.2 • Public • Published

env-alias

NPM MIT License Continuous Integration Coverage Status Dependabot Status

Define aliases for environment variables and bind them at runtime.

Rationale

Platform providers may have different names for related environment variables, and often developers rely on a particular name to be available, tying the code to the targeted deployment platform. This leads to lock-in, and makes it harder to deploy the application anywhere, breaking the first rule of the Twelve Factor App: one codebase, many deploys.

Environment variable aliasing helps with breaking this lock-in, as it is done not in the code, but in the environment itself:

# Assign DEST_BAR to the value of SOURCE_FOO at runtime
ENV_ALIAS_DEST_BAR='SOURCE_FOO'

Installation

$ yarn add env-alias
# or
$ npm i env-alias

Usage

Your environment could look like this:

# These are set by your hosting provider:
PROVIDER_GIT_COMMIT_ID
PROVIDER_DEPLOYMENT_ID

# But your app expects these:
MY_GIT_SHA1
MY_DEPLOYMENT_ID

# Declare aliased variables:
ENV_ALIAS_MY_GIT_SHA1='PROVIDER_GIT_COMMIT_ID'
ENV_ALIAS_MY_DEPLOYMENT_ID='PROVIDER_DEPLOYMENT_ID'

Then in your code:

import envAlias from 'env-alias'

envAlias({
  aliasPrefix: 'ENV_ALIAS_' // default prefix
})

const gitSha1 = process.env.MY_GIT_SHA1
const deployment = process.env.MY_DEPLOYMENT_ID

Configuration

env-alias accepts an optional configuration object with the following properties:

  • aliasPrefix: a string that will define the prefix to look for when resolving aliases. Defaults to ENV_ALIAS_.

    Anything after this prefix will become the aliased variable name (so don't forget the underscore).

List of aliases

envAlias will return the list of aliases it has found and processed:

import envAlias from 'env-alias'

const aliases = envAlias()
console.log(aliases)
[
  {
    "sourceName": "PROVIDER_GIT_COMMIT_ID",
    "destName": "MY_GIT_SHA1"
  },
  {
    "sourceName": "PROVIDER_DEPLOYMENT_ID",
    "destName": "MY_DEPLOYMENT_ID"
  }
]

Order of precedence

If a variable with the destination name is set, env-alias will not overwrite it. This allows overriding aliased definitions by explicitly setting the target variable:

APP_NAME="foo"

MY_APP_NAME="bar"

ENV_ALIAS_MY_APP_NAME="APP_NAME"

# MY_APP_NAME will be "bar"

License

MIT - Made with ❤️ by François Best - Donations welcome 🙏

Install

npm i env-alias

DownloadsWeekly Downloads

31

Version

1.0.2

License

MIT

Unpacked Size

8.47 kB

Total Files

5

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