@darkobits/env

A functional getter/parser for process.env.

Features

• Casts number-like values to numbers.
• Casts "true" and "false" to booleans.
• Parses JSON.
• Throws if process or process.env are non-objects.
• (Optional) Throw if a variable is undefined.

Install

$ npm i @darkobits/env

Use

This package's default export is a function with the following signature:

interface Env {
  (variableName: string, strict: boolean = false): any;
  has(variableName: string): boolean;
  eq(variableName: string, value: any, strict: boolean = false): boolean;
}

Keeping in mind that the values in process.env may only be strings, let's assume process.env looks like this:

{
  "FOO": "foo",
  "BAR": "42",
  "BAZ": "true",
  "QUX": "false",
  "JSON": "{\"kittens\": true}"
}

import env from '@darkobits/env';

env('FOO')         //=> 'foo'
typeof env('FOO')  //=> 'string'

env('BAR')         //=> 42
typeof env('BAR')  //=> 'number'

env('BAZ')         //=> true
typeof env('BAZ')  //=> 'boolean'

env('QUX')         //=> false
typeof env('BAZ')  //=> 'boolean'

env('JSON')        //=> {kittens: true}
typeof env('JSON') //=> 'object'

env('NOAP')        //=> undefined
env('NOAP', true)  //=> throws

// Throws if process.env has been tampered-with.
process.env = null;
env('FOO')         //=> throws

// Throws if process has been tampered-with, or if process doesn't exist.
process = null;
env('FOO')         //=> throws

env.has

This helper predicate is a shorthand for Object.keys(process.env).includes(x). It returns true if the provided variable name exists in process.env and false otherwise. Useful when you don't care what the value of a variable is, only whether it is set or not.

Using our example process.env object from above:

env.has('FOO') //=> true
env.has('UNICORNS') //=> false

env.eq

This helper predicate is a shorthand for env(variableName) === value. It returns true if the provided variable name exists in process.env and is equal to the provided value and false otherwise. Useful when you need to quickly test the value of an environment variable. A third strict argument may be set to true to cause env.eq to throw if the provided variable does not exist in process.env.

Note: When comparing against non-primitives (objects, arrays), env.eq will serialize the provided value and compare it against the serialized (re: string) form of the environment variable.

Using our example process.env object from above:

import env from '@darkobits/env';

env.eq('FOO', 'foo') //=> true
env.eq('BAR', 42)    //=> true
env.eq('BAR', null)  //=> false
env.eq('BAZ', true)  //=> true
env.eq('JSON', {kittens: true}) //=> true