Feature Request: Add debounce method

This is a feature request for adding a debounce function to the async module.

I always use a debounce function along with the Deno.watchFs method and I have seen it in other projects as well. So I think this is a useful function that could be added to deno/std.

I have already opened a PR with a first version of how the module could look like (#1006). I added it to the async module rn, but i’m not sure if that’s the best place.

Proposed typings:

declare interface DebouncedFunction<T extends Array<unknown>> {
  /** Calls the function with a delay. */
  (...args: T): void;
  /** Clears the debounce timeout without calling the debounced function. */
  clear(): void;
  /** Clears the debounce timeout with calling the debounced function immediately. */
  flush(): void;
  /** Returns a boolean wether a debounce call is pending or not. */
  readonly pending: boolean;
}

declare function debounce<T extends Array<any>>(
  func: (this: DebouncedFunction<T>, ...args: T) => void,
  wait: number,
): DebouncedFunction<T>;

Usage example:

import { debounce } from "https://deno.land/std/async/debounce.ts";

const log: DebouncedFunction<[string]> = debounce(
  (param: string) => console.log(param),
  200,
);

log("foo");
log("bar");
log("baz");
// wait 200ms ...
// output: baz

[c4spar]

I was just looking through the project to see if we have some conventions on how we name function types.

It seems that for properties and variables we mostly use fn as naming convention. For types and interfaces we mostly use the convention FooFunction.

File	Types
testing/bench.ts	BenchmarkFunction
datetime/tokenizer.ts	TestFunction, CallbackFunction
encoding/_yaml/parse.ts	CbFunction
log/handlers.ts	FormatterFunction
node/events.ts	GenericFunction, WrappedFunction
node/module.ts	RequireFunction
examples/xeval.ts	XevalFunc

So, i think we should go with DebouncedFunction to be consistent.

[wperron]

That sounds great, let’s go with that! thanks for the due diligence on this