Add timer class example

Author: tshemsedinov

JavaScript/4-order.js

@@ -59,3 +59,5 @@ fs.readFile('./4-order.js', 'utf8', () => {
 fs.readFile('./4-order.js', 'utf8', () => {
   console.log('callback #14 readFile');
 });
+
+console.log('main ended');

JavaScript/8-ref-unref.js

@@ -6,5 +6,6 @@ console.dir(timer);
 
 if (process.argv[2] === '--unref') timer.unref();
 console.dir(timer);
+
 if (process.argv[3] === '--ref') timer.ref();
 console.dir(timer);

JavaScript/b-timer.js

@@ -0,0 +1,45 @@
+'use strict';
+
+class Timer {
+  constructor(interval) {
+    this.interval = interval;
+    this.enabled = false;
+    this.listeners = [];
+    this.timer = null;
+  }
+  on(name, fn) {
+    if (name === 'timer') {
+      this.listeners.push(fn);
+    }
+  }
+  start() {
+    if (!this.enabled) {
+      this.enabled = true;
+      this.timer = setTimeout(() => {
+        this.enabled = false;
+        for (const fn of this.listeners) fn();
+      }, this.interval);
+    }
+  }
+  stop() {
+    if (this.enabled) {
+      clearTimeout(this.timer);
+      this.enabled = false;
+    }
+  }
+}
+
+// Uasge
+
+const timer1 = new Timer(2000);
+
+timer1.on('timer', () => {
+  console.log('Timer event 1');
+});
+
+timer1.on('timer', () => {
+  console.log('Timer event 2');
+});
+
+timer1.start();
+timer1.stop();