Many of the interfaces in the Obsidian lets you subscribe to events throughout the application, for example when the user makes changes to a file.
Any registered event handlers need to be detached whenever the plugin unloads. The safest way to make sure this happens is to use the [[registerEvent|registerEvent()]] method.
```ts
import { Plugin } from "obsidian";
export default class ExamplePlugin extends Plugin {
async onload() {
this.registerEvent(this.app.vault.on('create', () => {
console.log('a new file has entered the arena')
}));
}
}
```
## Timing events
If you want to repeatedly call a function with a fixed delay, use the [`window.setInterval()`](https://developer.mozilla.org/en-US/docs/Web/API/setInterval) function with the [[registerInterval|registerInterval()]] method.
The following example displays the current time in the status bar, updated every second:
```ts
import { moment, Plugin } from "obsidian";
export default class ExamplePlugin extends Plugin {
statusBar: HTMLElement;
async onload() {
this.statusBar = this.addStatusBarItem();
this.updateStatusBar();
this.registerInterval(
window.setInterval(() => this.updateStatusBar(), 1000)
);
}
updateStatusBar() {
this.statusBar.setText(moment().format("H:mm:ss"));
}
}
```
> [!tip] Date and time
> [Moment](https://momentjs.com/) is a popular JavaScript library for working with dates and time. Obsidian uses Moment internally, so you don't need to install it yourself. You can import it from the Obsidian API instead:
>
> ```ts
> import { moment } from "obsidian";
> ```