Tldraw/apps/docs/utils/debounce.ts

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1.1 KiB
TypeScript

/**
* Debounce a function.
*
* @example
*
* ```ts
* const A = debounce(myFunction, 1000)
* ```
*
* @public
* @see source - https://gist.github.com/ca0v/73a31f57b397606c9813472f7493a940
*/
export function debounce<T extends unknown[], U>(
callback: (...args: T) => PromiseLike<U> | U,
wait: number
) {
let state:
| undefined
| {
timeout: ReturnType<typeof setTimeout>
promise: Promise<U>
resolve: (value: U | PromiseLike<U>) => void
reject: (value: any) => void
latestArgs: T
} = undefined
const fn = (...args: T): Promise<U> => {
if (!state) {
state = {} as any
state!.promise = new Promise((resolve, reject) => {
state!.resolve = resolve
state!.reject = reject
})
}
clearTimeout(state!.timeout)
state!.latestArgs = args
state!.timeout = setTimeout(() => {
const s = state!
state = undefined
try {
s.resolve(callback(...s.latestArgs))
} catch (e) {
s.reject(e)
}
}, wait)
return state!.promise
}
fn.cancel = () => {
if (!state) return
clearTimeout(state.timeout)
}
return fn
}