@slimio/config
Advanced tools
SlimIO - Reactive JSON Configuration loader. This package is used in SlimIO core and addons to safely hot reload configuration upon JSON Schema.
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
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");
async function main() {
const cfg = new Config("./path/to/config.json");
await cfg.read();
console.log(cfg.get("loglevel")); // stdout: 5
// Observe (with an Observable Like) the update made to login property
cfg.observableOf("login").subscribe(console.log);
cfg.set("login", "admin");
// Payload getter will return a deepClone with all configuration properties
console.log(cfg.payload);
await cfg.close();
}
main().catch(console.error);
Note: config.json should exist (if not, it will throw an Error). Look at
createOnNoEntryoption for more information !
Configuration class is extended by a Node.js EventEmitter. The class can trigger several events:
| event name | description |
|---|---|
| configWritten | The configuration payload has been written on the local disk |
| watcherInitialized | The file watcher has been initialized (it will hot reload the configuration on modification) |
| reload | The configuration has been hot reloaded successfully |
| close | Event triggered when the configuration is asked to be closed |
This section describe how works the methods of Config class. For a complete definition, take a look at index.d.ts !
Create a new Config Object:
const cfg = new Config("./path/to/file.json", {
createOnNoEntry: true,
autoReload: true
});
Available options are:
| name | type | default value | description |
|---|---|---|---|
| createOnNoEntry | boolean | false | Create the file with default payload value if he doesn't exist on the local disk |
| writeOnSet | boolean | false | Write the file on the disk after each time .set() is called |
| autoReload | boolean | false | Setup hot reload of the configuration file |
| reloadDelay | number | 500ms | The delay to wait before hot reloading the configuration, it's a security to avoid event spamming |
| defaultSchema | plainObject | null | The default JSON Schema for the configuration |
Note: When no schema is provided, it will search for a file prefixed by
.schemawith the same config name.
Will trigger and read the local configuration (on disk). A default payload value can be provided in case the file doesn't exist !
const { strictEqual } = require("assert");
const cfg = new Config("./path/to/file.json");
strictEqual(cfg.configHasBeenRead, false); // true
await cfg.read();
strictEqual(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.
Warning When the file doesn't exist, the configuration is written at the next loop iteration (with lazyWriteOnDisk).
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.
We use the package node-watch to achieve the hot reload.
Get a value from a key (fieldPath). For example, let take a json payload with a root foo field.
const cfg = new Config("./path/to/file.json");
await cfg.read();
const fooValue = cfg.get("foo");
Under the hood the method work with
lodash.getfunction.
If the retrieved value is a JavaScript object, you can limit the depth by setting depth option.
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();
Under the hood the method work with
lodash.setfunction.
Observe a given configuration key with an Observable Like 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));
Write the configuration on the disk.
Write the configuration on the disk (only at the next event-loop iteration). Use the event configWritten to known when the configuration will be written.
const cfg = new Config("./config.json", {
createOnNoEntry: true
});
await cfg.read();
cfg.once("configWritten", () => {
console.log("Configuration written!");
});
cfg.lazyWriteOnDisk();
Close (and write on disk) the configuration (it will close the watcher and complete/clean all active observers subscribers).
Following properties are static members of Config class.
The default value is the following Object:
{
title: "CONFIG",
additionalProperties: true
}
MIT
0.13.0 (2019-01-31)
FAQs
SlimIO Reactive JSON Config loaded
The npm package @slimio/config receives a total of 2 weekly downloads. As such, @slimio/config popularity was classified as not popular.
We found that @slimio/config demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 2 open source maintainers collaborating on the project.
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