Move throttle and debounce from metasync

Refs: https://github.com/metarhia/metasync
Refs: #268

lib/async.js

@@ -46,4 +46,42 @@ const timeoutify = (promise, msec) =>
     );
   });
 
-module.exports = { toBool, timeout, delay, timeoutify };
+const throttle = (timeout, fn, ...args) => {
+  let timer;
+  let wait = false;
+
+  const execute = args
+    ? (...pars) => (pars ? fn(...args, ...pars) : fn(...args))
+    : (...pars) => (pars ? fn(...pars) : fn());
+
+  const delayed = (...pars) => {
+    timer = undefined;
+    if (wait) execute(...pars);
+  };
+
+  const throttled = (...pars) => {
+    if (!timer) {
+      timer = setTimeout(delayed, timeout, ...pars);
+      wait = false;
+      execute(...pars);
+    }
+    wait = true;
+  };
+
+  return throttled;
+};
+
+const debounce = (timeout, fn, ...args) => {
+  let timer;
+
+  const debounced = () => (args ? fn(...args) : fn());
+
+  const wrapped = () => {
+    if (timer) clearTimeout(timer);
+    timer = setTimeout(debounced, timeout);
+  };
+
+  return wrapped;
+};
+
+module.exports = { toBool, timeout, delay, timeoutify, throttle, debounce };

test/async.js

@@ -2,7 +2,14 @@
 
 const test = require('node:test');
 const assert = require('node:assert');
-const { toBool, timeout, delay, timeoutify } = require('..');
+const {
+  toBool,
+  timeout,
+  delay,
+  timeoutify,
+  throttle,
+  debounce,
+} = require('..');
 
 test('Async: toBool', async () => {
   const success = await Promise.resolve('success').then(...toBool);
@@ -67,3 +74,96 @@ test('Async: timeoutify', async () => {
     assert.ifError(new Error('Should not be executed'));
   }
 });
+
+test('Async: throttle', () => {
+  let callCount = 0;
+
+  const fn = (arg1, arg2, ...otherArgs) => {
+    assert.strictEqual(arg1, 'someVal');
+    assert.strictEqual(arg2, 4);
+    assert.strictEqual(otherArgs, []);
+    callCount++;
+  };
+
+  const throttledFn = throttle(1, fn, 'someVal', 4);
+
+  throttledFn();
+  assert.strictEqual(callCount, 1);
+  throttledFn();
+  throttledFn();
+  assert.strictEqual(callCount, 1);
+});
+
+test('Async: throttle merge args', () => {
+  let callCount = 0;
+
+  const fn = (arg1, arg2, ...otherArgs) => {
+    assert.strictEqual(arg1, 'someVal');
+    assert.strictEqual(arg2, 4);
+    assert.strictEqual(otherArgs, ['str']);
+    callCount++;
+  };
+
+  const throttledFn = throttle(1, fn, 'someVal', 4);
+
+  throttledFn('str');
+  assert.strictEqual(callCount, 1);
+  throttledFn('str');
+  throttledFn('str');
+  assert.strictEqual(callCount, 1);
+});
+
+test('Async: throttle without arguments', () => {
+  let callCount = 0;
+
+  const fn = (...args) => {
+    assert.strictEqual(args, []);
+    callCount++;
+  };
+
+  const throttledFn = throttle(1, fn);
+
+  throttledFn();
+  assert.strictEqual(callCount, 1);
+  throttledFn();
+  throttledFn();
+  assert.strictEqual(callCount, 1);
+});
+
+test('Async: debounce', async () => {
+  const { promise, resolve } = Promise.withResolvers();
+  let count = 0;
+
+  const fn = (arg1, arg2, ...otherArgs) => {
+    assert.strictEqual(arg1, 'someVal');
+    assert.strictEqual(arg2, 4);
+    assert.strictEqual(otherArgs, []);
+    count++;
+    resolve();
+  };
+
+  const debouncedFn = debounce(1, fn, 'someVal', 4);
+
+  debouncedFn();
+  debouncedFn();
+  assert.strictEqual(count, 0);
+  return promise;
+});
+
+test('Async: debounce without arguments', async () => {
+  const { promise, resolve } = Promise.withResolvers();
+  let count = 0;
+
+  const fn = (...args) => {
+    assert.strictEqual(args, []);
+    count++;
+    resolve();
+  };
+
+  const debouncedFn = debounce(1, fn);
+
+  debouncedFn();
+  debouncedFn();
+  assert.strictEqual(count, 0);
+  return promise;
+});