env-var
Verification, sanitization, and type coercion for environment variables in
Node.js. Particularly useful in TypeScript environments.
Install
Note: env-var requires Node version 8 or later.
npm
npm install env-var --save
yarn
yarn add env-var
Usage
In the example below we read the environment variable DB_PASSWORD and call
some functions to verify it satisfies our program's needs.
const env = require('env-var');
const PASSWORD = env.get('DB_PASSWORD')
.required()
.convertFromBase64()
.asString();
const PORT = env.get('PORT', 5432).asPortNumber()
TypeScript
import * as env from 'env-var';
const PORT: number = env.get('PORT').required().asIntPositive();
Benefits
Fail fast if your environment is misconfigured. Also,
this code without
env-var
would require multiple assert
calls, other logic, and be more
complex to understand as demonstrated here.
API
Structure:
EnvVarError()
This is the error class used to represent errors raised by this module. Sample
usage:
const env = require('env-var')
let value = null
try {
value = env.get('MISSING_VARIABLE').required().asString()
throw new Error('some other error')
} catch (e) {
if (e instanceof env.EnvVarError) {
console.log('we got an env-var error', e)
} else {
console.log('we got some error that wasn\'t an env-var error', e)
}
}
This function is useful if you're not in a typical Node.js environment, or for
testing. It allows you to generate an env-var instance that reads from the
given values
instead of the default process.env
.
const env = require('env-var').from({
API_BASE_URL: 'https://my.api.com/'
})
const apiUrl = mockedEnv.get('API_BASE_URL').asUrlString()
When calling from()
you can also pass an optional parameter containing
additional accessors that will be attached to any variables gotten by that
env-var instance.
Accessor functions must accept at least one argument:
{*} value
: The value that the accessor should process.
Important: Do not assume that value
is a string!
Example:
const { from } = require('env-var')
process.env.ADMIN = 'admin@example.com'
const env = from(process.env, {
checkEmail: (value) => {
const split = String(value).split('@')
if (split.length !== 2) {
throw new Error('must contain exactly one "@"')
}
return value
}
})
let validEmail = env.get('ADMIN').checkEmail()
The accessor function may accept additional arguments if desired; these must be
provided explicitly when the accessor is invoked.
For example, we can modify the checkEmail()
accessor from above so that it
optionally verifies the domain of the email address:
const { from } = require('env-var')
process.env.ADMIN = 'admin@example.com'
const env = from(process.env, {
checkEmail: (value, requiredDomain) => {
const split = String(value).split('@')
if (split.length !== 2) {
throw new Error('must contain exactly one "@"')
}
if (requiredDomain && (split[1] !== requiredDomain)) {
throw new Error(`must end with @${requiredDomain}`)
}
return value
}
})
let validEmail = env.get('ADMIN').checkEmail()
let invalidEmail = env.get('ADMIN').checkEmail('github.com')
This feature is also available for TypeScript users. The ExtensionFn
type is
expoed to help in the creation of these new accessors.
import { from, ExtensionFn, EnvVarError } from 'env-var'
process.env.ADMIN = 'admin@example.com'
const checkEmail: ExtensionFn<string> = (value) => {
const split = String(value).split('@')
if (split.length !== 2) {
throw new Error('must contain exactly one "@"')
}
return value
}
const env = from(process.env, {
checkEmail
})
env.get('ADMIN').checkEmail()
get([varname, [default]])
You can call this function 3 different ways:
const env = require('env-var')
const limit = env.get('SOME_LIMIT').asIntPositive()
const limit = env.get('SOME_LIMIT', '10').asIntPositive()
const allvars = env.get()
variable
A variable is returned by calling env.get
. It has the exposes the following
functions to validate and access the underlying value.
required(isRequired = true)
Ensure the variable is set on process.env. If the variable is not set or empty
this function will throw an EnvVarError
. If the variable is set it returns itself
so you can access the underlying variable.
Can be bypassed by passing false
, i.e required(false)
Full example:
const env = require('env-var')
const NODE_ENV = env.get('NODE_ENV').asString()
const PORT = env.get('PORT').required().asIntPositive()
const SECRET = env.get('SECRET', 'bad-secret').required(NODE_ENV === 'production').asString()
app.listen(PORT)
convertFromBase64()
Sometimes environment variables need to be encoded as base64. You can use this
function to convert them to UTF-8 strings before parsing them.
For example if we run the script script below, using the command DB_PASSWORD= $(echo -n 'secret_password' | base64) node
, we'd get the following results:
console.log(process.env.DB_PASSWORD)
const dbpass = env.get('DB_PASSWORD').convertFromBase64().asString()
asPortNumber()
Converts the value of the environment variable to a string and verifies it's
within the valid port range of 0-65535. As a result well known ports are
considered valid by this function.
asEnum(validValues: string[])
Converts the value to a string, and matches against the list of valid values.
If the value is not valid, an error will be raised describing valid input.
asInt()
Attempt to parse the variable to an integer. Throws an exception if parsing
fails. This is a strict check, meaning that if the process.env value is "1.2",
an exception will be raised rather than rounding up/down.
asIntPositive()
Performs the same task as asInt(), but also verifies that the number is
positive (greater than zero).
asIntNegative()
Performs the same task as asInt(), but also verifies that the number is
negative (less than zero).
asFloat()
Attempt to parse the variable to a float. Throws an exception if parsing fails.
asFloatPositive()
Performs the same task as asFloat(), but also verifies that the number is
positive (greater than zero).
asFloatNegative()
Performs the same task as asFloat(), but also verifies that the number is
negative (less than zero).
asString()
Return the variable value as a String. Throws an exception if value is not a
String. It's highly unlikely that a variable will not be a String since all
process.env entries you set in bash are Strings by default.
asBool()
Attempt to parse the variable to a Boolean. Throws an exception if parsing
fails. The var must be set to either "true", "false" (upper or lowercase),
0 or 1 to succeed.
asBoolStrict()
Attempt to parse the variable to a Boolean. Throws an exception if parsing
fails. The var must be set to either "true" or "false" (upper or lowercase) to
succeed.
asJson()
Attempt to parse the variable to a JSON Object or Array. Throws an exception if
parsing fails.
asJsonArray()
The same as asJson but checks that the data is a JSON Array, e.g [1,2].
asJsonObject()
The same as asJson but checks that the data is a JSON Object, e.g {a: 1}.
asArray([delimiter: string])
Reads an environment variable as a string, then splits it on each occurence of
the specified delimiter. By default a comma is used as the delimiter. For
example a var set to "1,2,3" would become ['1', '2', '3']. Example outputs for
specific values are:
- Reading
MY_ARRAY=''
results in []
- Reading
MY_ARRAY='1'
results in ['1']
- Reading
MY_ARRAY='1,2,3'
results in ['1', '2', '3']
asUrlString()
Verifies that the variable is a valid URL string and returns the validated
string. The validation is performed by passing the URL string to the
Node.js URL Constructor.
asUrlObject()
Verifies that the variable is a valid URL string using the same method as
asUrlString()
, but instead returns the resulting URL instance. For details
see the Node.js URL docs.
Examples
const env = require('env-var');
process.env.STRING = 'test';
process.env.INTEGER = '12';
process.env.BOOL = 'false';
process.env.JSON = '{"key":"value"}';
process.env.COMMA_ARRAY = '1,2,3';
process.env.DASH_ARRAY = '1-2-3';
const allVars = env.get();
const stringVar = env.get('STRING').required().asString();
const intVar = env.get('INTEGER').asInt();
const floatVar = env.get('FLOAT', '23.2').asFloat();
const boolVar = env.get('BOOL').required().asBool();
const jsonVar = env.get('JSON').asJson();
const commaArray = env.get('COMMA_ARRAY').asArray();
const commaArray = env.get('DASH_ARRAY').asArray('-');
const enumVal = env.get('ENVIRONMENT').asEnum(['dev', 'test', 'live'])
Contributing
Contributions are welcomed. If you'd like to discuss an idea open an issue, or a
PR with an initial implementation.
If you want to add a new global accessor, it's easy. Add a file to
lib/accessors
, with the name of the type e.g add a file named number-zero.js
into that folder and populate it with code following this structure:
module.exports = function numberZero (environmentValue) {
const val = parseInt(environmentValue)
if (val === 0) {
return ret;
} else {
throw new Error('should be zero')
}
}
Next update the accessors
Object in getVariableAccessors()
in
lib/variable.js
to include your new module. The naming convention should be of
the format "asTypeSubtype", so for our number-zero
example it would be done
like so:
asNumberZero: generateAccessor(container, varName, defValue, require('./accessors/number-zero')),
Once you've done that, add some unit tests and use it like so:
env.get('SOME_NUMBER').asNumberZero()
Contributors
- @caccialdo
- @evanshortiss
- @gabrieloczkowski
- @hhravn
- @itavy
- @MikeyBurkman
- @pepakriz
- @rmblstrp