/
debounce.ts
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/
debounce.ts
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// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
/**
* A debounced function that will be delayed by a given `wait`
* time in milliseconds. If the method is called again before
* the timeout expires, the previous call will be aborted.
*/
export interface DebouncedFunction<T extends Array<unknown>> {
(...args: T): void;
/** Clears the debounce timeout and omits calling the debounced function. */
clear(): void;
/** Clears the debounce timeout and calls the debounced function immediately. */
flush(): void;
/** Returns a boolean wether a debounce call is pending or not. */
readonly pending: boolean;
}
/**
* Creates a debounced function that delays the given `func`
* by a given `wait` time in milliseconds. If the method is called
* again before the timeout expires, the previous call will be
* aborted.
*
* ```
* import { debounce } from "https://deno.land/std/async/mod.ts";
*
* const log = debounce(
* (event: Deno.FsEvent) =>
* console.log("[%s] %s", event.kind, event.paths[0]),
* 200,
* );
*
* for await (const event of Deno.watchFs("./")) {
* log(event);
* }
* ```
*
* @param fn The function to debounce.
* @param wait The time in milliseconds to delay the function.
*/
// deno-lint-ignore no-explicit-any
export function debounce<T extends Array<any>>(
fn: (this: DebouncedFunction<T>, ...args: T) => void,
wait: number,
): DebouncedFunction<T> {
let timeout: number | null = null;
let flush: (() => void) | null = null;
const debounced: DebouncedFunction<T> = ((...args: T): void => {
debounced.clear();
flush = (): void => {
debounced.clear();
fn.call(debounced, ...args);
};
timeout = setTimeout(flush, wait);
}) as DebouncedFunction<T>;
debounced.clear = (): void => {
if (typeof timeout === "number") {
clearTimeout(timeout);
timeout = null;
flush = null;
}
};
debounced.flush = (): void => {
flush?.();
};
Object.defineProperty(debounced, "pending", {
get: () => typeof timeout === "number",
});
return debounced;
}