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Transforming values

Transformers are functions that converts value from provider. @pallad/config has few built-in transformers but you can write your own, which is just any function that accepts input value and returns transformed one.


Converts value to int. Throws an error if cannot be converted.

import {env, type} from '@pallad/config';

env('FOO', {transformer:});


Converts value to number. Throws an error if cannot be converted.

import {env, type} from '@pallad/config';

env('FOO', {transformer: type.number});


Converts value to boolean. Throws an error if cannot be converted. Uses glorious yn library so boolean-ish values like yes, no, y, on, off etc are allowed.

import {env, type} from '@pallad/config';

env('FOO', {transformer: type.bool});


Ensures that value is a string and got trimmed from whitespaces at the beginning and the end.

import {env, type} from '@pallad/config';

env('FOO', {transformer: type.string});


Ensures that value is an URL, throws an error otherwise.

import {env, type} from '@pallad/config';

env('FOO', {transformer: type.url});

You can enforce certain protocols like http or https

import {env, type} from '@pallad/config';

env('FOO', {transformer: type.url.options({protocols: ['http', 'https']})});

Splitting by separator

Splits value into an array by given seperator (by default ","). All array values are trimmed and empty values got removed.

import {env, type} from '@pallad/config';

env('FOO', {transformer: type.split});

Custom separator

import {env, type} from '@pallad/config';

env('FOO', {transformer:{separator: ':'})});

Uses custom separator and additionally transforms every array value to int

import {env, type} from '@pallad/config';

env('FOO', {
separator: ':',

Protecting from accidental leak via @pallad/secret

@pallad/secret is a tool that wraps any value and prevents it from being logged, converted to string, inspected etc. Therefore it will help protect your configuration and secret from accidental leak.

Wrapping value with Secret

import {env} from '@pallad/config';
import {secret} from '@pallad/config';

env('FOO', {transformer: secret});

Converts value to int and wraps with secret

import {env, type} from '@pallad/config';
import {protect} from '@pallad/config';

env('FOO', {transformer: protect(});

Custom transformer

As mentioned before, transformer is just a simple mapping function that accepts loaded value as input and returns transformed value.

import {env} from '@pallad/config';

function upperCase(value: string) {
// you can validate input value and throw an error if something is wrong
return value.toUpperCase();

env('FOO', {transformer: upperCase});