@@ -0,0 +1,56 @@
+'use strict';
+
+class Proactor {
+  #tasks = [];
+
+  enqueue(fn, callback) {
+    this.#tasks.push({ fn, callback });
+  }
+
+  start() {
+    while (this.#tasks.length) {
+      const tasks = this.#tasks.splice(0);
+      this.#next(tasks, 0);
+    }
+  }
+
+  #next(tasks, offset) {
+    if (offset >= tasks.length) return;
+    const handler = tasks[offset];
+    handler.fn((err, data) => {
+      handler.callback(err, data);
+    });
+    this.#next(tasks, offset + 1);
+  }
+}
+
+// Usage
+
+const eventLoop = new Proactor();
+
+const fakeAsyncRead = (name, callback) => {
+  const delay = Math.random() * 1000;
+  const fn = (done) => {
+    setTimeout(() => {
+      done(null, 'FILE DATA');
+    }, delay);
+  };
+  eventLoop.enqueue(fn, callback);
+};
+
+fakeAsyncRead('File A', (err, data) => {
+  if (err) console.error(`[Proactor] File A: failed "${err.message}"`);
+  else console.log(`[Proactor] File A: done "${data}"`);
+});
+
+fakeAsyncRead('File B', (err, data) => {
+  if (err) console.error(`[Proactor] File B: failed "${err.message}"`);
+  else console.log(`[Proactor] File B: done "${data}"`);
+});
+
+fakeAsyncRead('File C', (err, data) => {
+  if (err) console.error(`[Proactor] File C: failed "${err.message}"`);
+  else console.log(`[Proactor] File C: done "${data}"`);
+});
+
+eventLoop.start();
@@ -0,0 +1,56 @@
+'use strict';
+
+class Proactor {
+  #tasks = [];
+
+  enqueue(fn, callback) {
+    this.#tasks.push({ fn, callback });
+  }
+
+  start() {
+    if (!this.#tasks.length) return;
+    const tasks = this.#tasks.splice(0);
+    this.#phase(tasks);
+  }
+
+  #phase(tasks) {
+    let counter = tasks.legth;
+    for (const task of tasks) {
+      task.fn((err, data) => {
+        task.callback(err, data);
+        if (--counter === 0) this.start();
+      });
+    }
+  }
+}
+
+// Usage
+
+const eventLoop = new Proactor();
+
+const fakeAsyncRead = (name, callback) => {
+  const delay = Math.random() * 1000;
+  const fn = (done) => {
+    setTimeout(() => {
+      done(null, 'FILE DATA');
+    }, delay);
+  };
+  eventLoop.enqueue(fn, callback);
+};
+
+fakeAsyncRead('File A', (err, data) => {
+  if (err) console.error(`[Proactor] File A: failed "${err.message}"`);
+  else console.log(`[Proactor] File A: done "${data}"`);
+});
+
+fakeAsyncRead('File B', (err, data) => {
+  if (err) console.error(`[Proactor] File B: failed "${err.message}"`);
+  else console.log(`[Proactor] File B: done "${data}"`);
+});
+
+fakeAsyncRead('File C', (err, data) => {
+  if (err) console.error(`[Proactor] File C: failed "${err.message}"`);
+  else console.log(`[Proactor] File C: done "${data}"`);
+});
+
+eventLoop.start();