EventEmitter class

tshemsedinov · tshemsedinov · commit 074dbd751a32 · 2019-06-02T17:51:56.000+03:00
diff --git a/JavaScript/b-class.js b/JavaScript/b-class.js
@@ -0,0 +1,120 @@
+'use strict';
+
+class EventEmitter {
+  constructor() {
+    this.events = new Map();
+    this.wrappers = new Map();
+  }
+
+  on(name, fn) {
+    const event = this.events.get(name);
+    if (event) event.add(fn);
+    else this.events.set(name, new Set([fn]));
+  }
+
+  once(name, fn) {
+    const wrapper = (...args) => {
+      this.remove(name, wrapper);
+      fn(...args);
+    };
+    this.wrappers.set(fn, wrapper);
+    this.on(name, wrapper);
+  }
+
+  emit(name, ...args) {
+    const event = this.events.get(name);
+    if (!event) return;
+    for (const fn of event.values()) {
+      fn(...args);
+    }
+  }
+
+  remove(name, fn) {
+    const event = this.events.get(name);
+    if (!event) return;
+    if (event.has(fn)) {
+      event.delete(fn);
+      return;
+    }
+    const wrapper = this.wrappers.get(fn);
+    if (wrapper) {
+      event.delete(wrapper);
+      if (event.size === 0) this.events.delete(name);
+    }
+  }
+
+  clear(name) {
+    if (name) this.events.delete(name);
+    else this.events.clear();
+  }
+
+  count(name) {
+    const event = this.events.get(name);
+    return event ? event.size : 0;
+  }
+
+  listeners(name) {
+    const event = this.events.get(name);
+    return new Set(event);
+  }
+
+  names() {
+    return [...this.events.keys()];
+  }
+}
+
+// Usage
+
+const ee = new EventEmitter();
+
+// on and emit
+
+ee.on('e1', data => {
+  console.dir(data);
+});
+
+ee.emit('e1', { msg: 'e1 ok' });
+
+// once
+
+ee.once('e2', data => {
+  console.dir(data);
+});
+
+ee.emit('e2', { msg: 'e2 ok' });
+ee.emit('e2', { msg: 'e2 not ok' });
+
+// remove
+
+const f3 = data => {
+  console.dir(data);
+};
+
+ee.on('e3', f3);
+ee.remove('e3', f3);
+ee.emit('e3', { msg: 'e3 not ok' });
+
+// count
+
+ee.on('e4', () => {});
+ee.on('e4', () => {});
+console.log('e4 count', ee.count('e4'));
+
+// clear
+
+ee.clear('e4');
+ee.emit('e4', { msg: 'e4 not ok' });
+ee.emit('e1', { msg: 'e1 ok' });
+
+ee.clear();
+ee.emit('e1', { msg: 'e1 not ok' });
+
+// listeners and names
+
+ee.on('e5', () => {});
+ee.on('e5', () => {});
+ee.on('e6', () => {});
+ee.on('e7', () => {});
+
+console.log('listeners', ee.listeners('e5'));
+console.log('names', ee.names());
