env-to-class

Load process.env into class instance by convention and validate with class-validator annotations

Example classes and corresponding environment variable names that will be loaded

class Nested {
   @IsString()
   foo: string // QUX_FOO

   @IsInt()
   barBaz: number // QUX_BAR_BAZ
}

class Cls {
   @ValidateNested
   qux: Nested = new Nested() // Default values are necessary for nested class fields

   @IsBoolean()
   quux: boolean // QUUX
}

Install

1. Install this package:

   npm install -S node-env-to-class

2. reflect-metadata shim is required, install it too:

   npm install reflect-metadata --save

   and make sure to import it in a global place, like app.ts:

   import 'reflect-metadata';

3. ES6 features are used, if you are using old version of node.js you may need to install es6-shim:

   npm install -S es6-shim

   and import it in a global place like app.ts:

   import 'es6-shim';

Usage

Define the classes and annotate with class-validator type decorators:

import {
   IsBoolean,
   IsInt,
   IsNumber,
   IsString,
   ValidateNested,
} from 'class-validator'

class Nested {
   @IsString()
   str: string = 'str-default'

   @IsInt()
   int: number = 123

   @IsNumber()
   float: number = 0.123

   @IsBoolean()
   bool: boolean = true
}

class Parent {
   @IsString()
   strParent!: string

   @IsInt()
   intParent!: number

   @IsNumber()
   floatParent: number = 0.321

   @IsBoolean()
   boolParent = false

   @ValidateNested()
   nestedParent: Nested = new Nested() // Default values are necessary for nested class fields
}

class Child extends Parent {
   @IsString()
   strChild: string = 'str-child-default'

   @IsInt()
   intChild: number = 321

   @IsNumber()
   floatChild!: number

   @IsBoolean()
   boolChild!: boolean

   @ValidateNested()
   nestedChild: Nested = new Nested() // Default values are necessary for nested class fields
}

❗ Note that both the TypeScript type annotations and the class-validator decorators are required. Default values are necessary for nested class fields.

Then use envToClass to load process.env into a class instance:

const [errs, c] = envToClass(Child)
if (errs.length) {
  console.log('Validation error:', errs)
} else {
  console.log('Loaded class:', c)
}

Set the envPrefix option to load from prefixed environment variable names such as PREFIX_ENV_NAME:

const [errs, c] = envToClass(Child, undefined, { envPrefix: 'PREFIX' })

classToEnv will override the existing values in the supplied class instance or the default values in the new class instance by default. To keep the existing values, set the overrideExistingValues option to true:

const [errs, c] = envToClass(Child, undefined, {
   overrideExistingValues: false,
})
if (errs.length) {
  console.log('Validation error:', errs)
} else {
  console.log('Loaded class:', c)
}

See Options for all the options.

license

MIT © Nex Zhu