std/async/unstable_throttle_test.ts

// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
import {
  assertEquals,
  assertGreater,
  assertLess,
  assertNotEquals,
  assertStrictEquals,
} from "@std/assert";
import { throttle, type ThrottledFunction } from "./unstable_throttle.ts";
import { delay } from "./delay.ts";

Deno.test("throttle() handles called", async () => {
  let called = 0;
  const t = throttle(() => called++, 100);
  assertEquals(t.throttling, false);
  assertEquals(t.lastExecution, NaN);
  t();
  const { lastExecution } = t;
  t();
  t();
  assertLess(Math.abs(t.lastExecution - Date.now()), 100);
  assertEquals(called, 1);
  assertEquals(t.throttling, true);
  assertEquals(t.lastExecution, lastExecution);
  await delay(200);
  assertEquals(called, 1);
  assertEquals(t.throttling, false);
  assertEquals(t.lastExecution, lastExecution);
  t();
  assertEquals(called, 2);
  assertEquals(t.throttling, true);
  assertGreater(t.lastExecution, lastExecution);
});

Deno.test("throttle() handles cancelled", () => {
  let called = 0;
  const t = throttle(() => called++, 100);
  t();
  t();
  t();
  assertEquals(called, 1);
  assertEquals(t.throttling, true);
  assertNotEquals(t.lastExecution, NaN);
  t.clear();
  assertEquals(called, 1);
  assertEquals(t.throttling, false);
  assertEquals(t.lastExecution, NaN);
});

Deno.test("debounce() handles flush", () => {
  let called = 0;
  let arg = "";
  const t = throttle((_arg) => {
    arg = _arg;
    called++;
  }, 100);
  t("foo");
  t("bar");
  t("baz");
  assertEquals(called, 1);
  assertEquals(arg, "foo");
  assertEquals(t.throttling, true);
  assertNotEquals(t.lastExecution, NaN);
  for (const _ of [1, 2]) {
    t.flush();
    assertEquals(called, 2);
    assertEquals(arg, "baz");
    assertEquals(t.throttling, false);
    assertEquals(t.lastExecution, NaN);
  }
});

Deno.test("throttle() handles params and context", async () => {
  const params: Array<string | number> = [];
  const t: ThrottledFunction<[string, number]> = throttle(
    function (param1: string, param2: number) {
      params.push(param1);
      params.push(param2);
      assertStrictEquals(t, this);
    },
    100,
  );
  t("foo", 1);
  t("bar", 1);
  t("baz", 1);
  // @ts-expect-error Argument of type 'number' is not assignable to parameter of type 'string'.
  t(1, 1);
  assertEquals(params, ["foo", 1]);
  assertEquals(t.throttling, true);
  await delay(200);
  assertEquals(params, ["foo", 1]);
  assertEquals(t.throttling, false);
});