@slimio/config

Config

SlimIO - Reactive JSON Config loader

Features

• Hot-reloading of configuration
• Reactive with observable key(s)
• Safe with JSON Schema validation

Getting Started

This package is available in the Node Package Repository and can be easily installed with npm or yarn.

$ npm i @slimio/config
# or
$ yarn add @slimio/config

Usage example

Create a simple json file for your project (As below)

{
    "loglevel": 5,
    "logsize": 4048,
    "login": "administrator"
}

Now create a new Configuration instance and read it

const Config = require("@slimio/config");

const cfg = new Config("./path/to/config.json");
cfg.read().then(() => {
    console.log(cfg.get("loglevel")); // stdout: 5
}).catch(console.error);

API

constructor(configFilePath: string, options?: Config.ConstructorOptions)

Create a new Configuration instance

const options = { autoReload: true };
const cfg = new Config("./path/to/file.json", options);

Available options are

interface ConstructorOptions {
    createOnNoEntry?: boolean;
    writeOnSet?: boolean;
    autoReload?: boolean;
    reloadDelay?: number;
    defaultSchema?: object;
}

read(defaultPayload?: T): Promise;

Will trigger and read the local configuration (on disk).

const cfg = new Config("./path/to/file.json");
assert.equal(cfg.configHasBeenRead, false); // true
await cfg.read();
assert.equal(cfg.configHasBeenRead, true); // true

Retriggering the method will made an hot-reload of all properties. For a cold reload you will have to close the configuration before.

setupAutoReload(): void;

Setup hot reload (with a file watcher). This method is automatically triggered if the Configuration has been created with the option autoReload set to true.

get(fieldPath: string): H

Get a value from a key (field path).

For example, image a json file with a foo field

const cfg = new Config("./path/to/file.json");
await cfg.read();
const fooValue = cfg.get("foo");

set(fieldPath: string, fieldValue: H): void;

Set a given field in the configuration

const cfg = new Config("./config.json", {
    createOnNoEntry: true
});

await cfg.read({ foo: "bar" });
cfg.set("foo", "hello world!");
await cfg.writeOnDisk();

observableOf(fieldPath: string): ObservableLike;

Observe a given configuration key with an Observable object!

const { writeFile } = require("fs").promises;
const cfg = new Config("./config.json", {
    autoReload: true,
    createOnNoEntry: true
});
await cfg.read({ foo: "bar" });

// Observe initial and next value(s) of foo
cfg.observableOf("foo").subscribe(console.log);

// Re-write local config file
const newPayload = { foo: "world" };
await writeFile("./config.json", JSON.stringify(newPayload, null, 4));

writeOnDisk(): Promise

Write the configuration on the disk

close(): Promise

Close (and write on disk) the configuration (it will close the watcher and clean all active observers).