once
Creates a function that can only be executed once; subsequent calls return the result of the first execution.
Syntax
typescript
once<T extends (...args: any[]) => any>(callback: T): (...args: Parameters<T>) => ReturnType<T>Parameters
| Name | Type | Description |
|---|---|---|
callback | T | Function to be executed only once. |
Returns
| Type | Description |
|---|---|
(...args: Parameters<T>) => ReturnType<T> | Function that executes callback only on the first call. |
Example
typescript
let count = 0;
const incrementOnce = once(() => ++count);
incrementOnce(); // 1
incrementOnce(); // 1Notes
- Throws a
TypeErrorif the argument is not a function. - Useful for initializations, one-time events, or idempotent operations.