Envalid is a small library for validating and accessing environment variables in Node.js (v8.12 or later) programs, aiming to:
- ensure that your program only runs when all of its environment dependencies are met
- give you executable documentation about the environment your program expects to run in
- give you an immutable API for your environment variables, so they don't change from under you while the program is running
cleanEnv()
returns a sanitized, immutable environment object, and accepts three
positional arguments:
environment
- An object containing your env vars (eg.process.env
)validators
- An object that specifies the format of required vars.options
- An (optional) object, which supports the following keys:strict
- (default:false
) Enable more rigorous behavior. See "Strict Mode" belowreporter
- Pass in a function to override the default error handling and console output. Seesrc/reporter.js
for the default implementation.transformer
- A function used to transform the cleaned environment object before it is returned fromcleanEnv
dotEnvPath
- (default:'.env'
) Path to the file that is parsed by dotenv to optionally load more env vars at runtime. Passnull
if you want to skipdotenv
processing entirely and only load fromprocess.env
.
By default, cleanEnv()
will log an error message and exit if any required
env vars are missing or invalid.
const envalid = require('envalid')
const { str, email, json } = envalid
const env = envalid.cleanEnv(process.env, {
API_KEY: str(),
ADMIN_EMAIL: email({ default: 'admin@example.com' }),
EMAIL_CONFIG_JSON: json({ desc: 'Additional email parameters' })
})
// Read an environment variable, which is validated and cleaned during
// and/or filtering that you specified with cleanEnv().
env.ADMIN_EMAIL // -> 'admin@example.com'
// Envalid parses NODE_ENV automatically, and provides the following
// shortcut (boolean) properties for checking its value:
env.isProduction // true if NODE_ENV === 'production'
env.isTest // true if NODE_ENV === 'test'
env.isDev // true if NODE_ENV === 'development'
For an example you can play with, clone this repo and see the example/
directory.
Node's process.env
only stores strings, but sometimes you want to retrieve other types
(booleans, numbers), or validate that an env var is in a specific format (JSON,
url, email address). To these ends, the following validation functions are available:
str()
- Passes string values through, will ensure an value is present unless adefault
value is given. Note that an empty string is considered a valid value - if this is undesirable you can easily create your own validator (see below)bool()
- Parses env var strings"1", "0", "true", "false", "t", "f"
into booleansnum()
- Parses an env var (eg."42", "0.23", "1e5"
) into a Numberemail()
- Ensures an env var is an email addresshost()
- Ensures an env var is either a domain name or an ip address (v4 or v6)port()
- Ensures an env var is a TCP port (1-65535)url()
- Ensures an env var is a url with a protocol and hostnamejson()
- Parses an env var withJSON.parse
Each validation function accepts an (optional) object with the following attributes:
choices
- An Array that lists the admissable parsed values for the env var.default
- A fallback value, which will be used if the env var wasn't specified. Providing a default effectively makes the env var optional.devDefault
- A fallback value to use only whenNODE_ENV
is not'production'
. This is handy for env vars that are required for production environments, but optional for development and testing.desc
- A string that describes the env var.example
- An example value for the env var.docs
- A url that leads to more detailed documentation about the env var.
You can easily create your own validator functions with envalid.makeValidator()
. It takes
a function as its only parameter, and should either return a cleaned value, or throw if the
input is unacceptable:
const { makeValidator, cleanEnv } = require('envalid')
const twochars = makeValidator(x => {
if (/^[A-Za-z]{2}$/.test(x)) return x.toUpperCase()
else throw new Error('Expected two letters')
})
const env = cleanEnv(process.env, {
INITIALS: twochars()
});
You can, and should, also provide a type
with your validator. This can be exposed by tools
to help other developers better understand you configuration options.
To add it, pass a string with the name as the second argument to makeValidator
.
const { makeValidator } = require('envalid')
const twochars = makeValidator(x => {
if (/^[A-Za-z]{2}$/.test(x)) return x.toUpperCase()
else throw new Error('Expected two letters')
}, 'twochars')
By default, if any required environment variables are missing or have invalid
values, envalid will log a message and call process.exit(1)
. You can override
this behavior by passing in your own function as options.reporter
. For example:
const env = cleanEnv(process.env, myValidators, {
reporter: ({ errors, env }) => {
emailSiteAdmins('Invalid env vars: ' + Object.keys(errors))
}
})
Additionally, envalid exposes EnvError
and EnvMissingError
, which can be checked in case specific error handling is desired:
const env = cleanEnv(process.env, myValidators, {
reporter: ({ errors, env }) => {
errors.forEach(err => {
if (err instanceof envalid.EnvError) {
...
} else if (err instanceof envalid.EnvMissingError) {
...
} else {
...
}
});
}
})
By passing the { strict: true }
option, envalid gives you extra tight guarantees
about the cleaned env object:
- The env object will only contain the env vars that were specified by your
validators
. - Any attempt to access an invalid/missing property on the env object will cause a thrown error.
- Any attempt to mutate the cleaned env object will cause a thrown error.
Envalid wraps the very handy dotenv package,
so if you have a .env
file in your project, envalid will read and validate the
env vars from that file as well.
When using Envalid within React Native the dotenv
integration will not work, and the dotEnvPath
option will be ignored.
Envalid can be used within React Native with a custom reporter.
Instead of dotenv
react-native-config can be used to read the configuration.
Example:
const reactNativeConfig = require('react-native-config')
const rawConfig = reactNativeConfig.default
const validatedConfig = envalid.cleanEnv(
rawConfig,
{
// validators
},
{
dotEnvPath: null,
reporter: ({ errors = {}, env = {} }) => {
// handle errors
},
},
)
When using Envalid within browsers the dotenv
integration will not work, and the dotEnvPath
option will be ignored.
A helper function called testOnly
is available, in case you need an default env var only when
NODE_ENV=test
. It should be used along with devDefault
, for example:
const env = cleanEnv(process.env, {
SOME_VAR: envalid.str({devDefault: testOnly('myTestValue')})
})
For more context see this issue.