deno-environment

Deno package for environment variables management.

Currently, Deno exposes environment variables through Deno.env. This package is for converting environment variables to expected types.

Exports are:

StringValue

Typescript string type. It checks if the environment value exists and does nothing with It.

NumberValue

Typescript number type. Converts env value to number.

IntValue

Integer type. Converts the environment variable to a number as well as NumberValue, but checks if the environment variable can be converted to integer.

BooleanValue

Typescript boolean type. Converts the environment variable to a boolean from string 'true' or 'false'.

EnvValue

Is a generic abstract class that must be extended in this way:

interface MyType {
  title: string;
  tome: number;
  isRead: boolean;
}

class MyType extends EnvValue<MyType> {
  protected mapper(rawValue: string): MyType {
    return JSON.parse(rawValue);
  }
}

So the raw env value could be '{"title": "Harry Potter", "tome": 1, "isRead": false}'. And the Environment converter can use JSON parser to do all the work.

Examples

Let’s imagine we have the environment variable port with value 8080. We could access that in this way:

const port = Number(Deno.env.get('port'));

But what if this environment variable is missing? We should check It first:

const portString = Deno.env.get('port');
const portNumber = Number(portString);

if (portNumber === undefined) {
  throw new Error('port number is missing');
}

if (Number.isNaN(portNumber)) {
  throw new Error('Incorrect port variable');
}

This routine could be easily done with this:

const portNumber = new IntValue('port').get();

Please, note

If a particular variable is not convertible, .get() method throws the exception.

Importing the module

mod.ts is an entrypoint, other files should not be used.

Tests

deno test --allow-env