# Scheduler
[](https://github.com/SlimIO/is/commit-activity)
[](https://snyk.io//test/github/SlimIO/Scheduler?targetFile=package.json)
Scheduler class are used by SlimIO Addons to schedule the execution of registered callbacks.
> ⚠️ Scheduler class are not designed to be precision timer (they are not a replacement of Node.js timers!).
## Requirements
- [Node.js](https://nodejs.org/en/) v10 or higher
## Getting Started
This package is available in the Node Package Repository and can be easily installed with [npm](https://docs.npmjs.com/getting-started/what-is-npm) or [yarn](https://yarnpkg.com).
```bash
$ npm i @slimio/scheduler
# or
$ yarn add @slimio/scheduler
```
## Usage example
Scheduler are often use with SlimIO Addon(s) and are not designed to be used out of the SlimIO agent.
```js
const Addon = require("@slimio/addon");
const Scheduler = require("@slimio/scheduler");
// Create your Addon
const myAddon = new Addon("myAddon");
// Create a sayHello function (our callback).
async function sayHello() {
console.log("hello world!");
}
async function midnightJob() {
console.log("executing at midnight!");
}
// Register "sayHello" callback and ask to schedule it every second (so it will be executed every second by Addon).
myAddon.registerCallback(sayHello)
.schedule(new Scheduler({ interval: 1 }));
// Register "midnightJob" callback and schedule it every 24 hours at midnight
myAddon.registerCallback(midnightJob)
.schedule(new Scheduler({ interval: 86_400, startDate: Scheduler.dateAtHours(24) }));
module.exports = myAddon;
```
## API
constructor(options?: CallbackScheduler.ConstructorOptions)
Construct a new Scheduler.
```js
const myScheduler = new Scheduler({
interval: 1250,
intervalUnitType: Scheduler.Types.Milliseconds
});
```
Available options are the following:
| argument name | type | default value | description |
| --- | --- | --- | --- |
| interval | number | 36000 | Default timer interval (in second if defaultType is not set) |
| startDate | date | Date.now() | The start date of the timer, dont set the property if you want the timer to start immediately |
| executeOnStart | boolean | false | The timer will return **true** on the very first walk() if this option is true |
| intervalUnitType | AvailableTypes | Types.seconds | Set the type of the interval |
Available types are:
```ts
interface AvailableTypes {
Milliseconds: "millisecond",
Seconds: "second"
}
```
dateAtHours(hours?: number, minutes?: number, seconds?: number): Date
Create a "Date" Object with some given **hours**, **minutes** and **seconds**. By default all of these are assigned to `0`.
```js
const Scheduler = require("@slimio/scheduler");
const myDate = Scheduler.dateAtHours(10, 1, 1);
console.log(myDate.toString()); // stdout myDate with 10 hours, 1 minutes, 1 seconds and 0 milliseconds
// Same as
const myJSDate = new Date();
myJSDate.setHours(10, 1, 1, 0);
```
reset(): void
Reset the Scheduler (it will reset inner timestamp). This method is automatically called by the `walk()` method.
walk(): boolean
Walk the Scheduler. It will return `false` if the time is not elapsed and `true` if the time has been elapsed. When true is returned, the timer is automatically resetted !
Workflow of walk() method
Available Types
Scheduler support both `Seconds` and `Milliseconds` types.
```ts
interface Types {
Milliseconds: "millisecond",
Seconds: "second"
}
```
It's recommanded to set the type at the initialization of the Scheduler. (Avoir updating the type on the fly).
```js
const timer = new Scheduler({
interval: 500, // Ms
intervalUnitType: Scheduler.Types.Milliseconds
});
timer.type = Scheduler.Types.Seconds;
```