Function when

when(predicate, fn, options?): (() => void)
Automatically calls the given function whenever the given predicate evaluates to true.
Parameters
- predicate: (() => boolean)
  The predicate that should be evaluated.
  - - (): boolean
    - Returns boolean
- fn: (() => void)
  The function to be called when the predicate evaluates to true.
  - - (): void
    - Returns void
- Optional options: {
      delay: number;
      signal: AbortSignal;
      timeout: number;
  }
  Optional options.
  - delay: number
    The number of milliseconds to wait before calling the function.
  - signal: AbortSignal
    An AbortSignal to cancel the function call.
  - timeout: number
    The number of milliseconds to wait before timing out.
Returns (() => void)
A function that can be called to unsubscribe the callback function from changes in the tracked dependencies.
- - (): void
  - Returns void
Example
```
const a = atom(0, { name: "a" });
let foo = 0;

when(
    () => a.value > 3,
    () => {
        foo++;
    }
);

a.value = 2; // foo = 0
a.value = 3; // foo = 0
a.value = 4; // foo = 1
a.value = 5; // foo = 1
a.value = 3; // foo = 1
a.value = 4; // foo = 2
a.value = 5; // foo = 2
```
- Defined in src/api/api.js:201