modify event code

Author: wangding

08-event/01-event-emitter.js

@@ -1,6 +1,6 @@
 #!/usr/bin/env node
 
-const EventEmitter = require('events').EventEmitter,
+const { EventEmitter } = require('events'),
       log          = console.log,
       e            = new EventEmitter();
 

08-event/02-dog.js

@@ -1,4 +1,4 @@
-const EventEmitter = require('events').EventEmitter;
+const { EventEmitter } = require('events');
 
 class Dog extends EventEmitter {
   constructor(name, energy) {

08-event/07-prd-csm.js

@@ -24,34 +24,39 @@ class Queue extends EventEmitter {
   #data = [];
 }
 
-let queue = new Queue();
-
 class Producer {
-  constructor() {}
+  constructor(queue) {
+    this.#queue = queue;
+  }
+
   create(data){
     log('+ prd create:', data);
-    queue.write(data);
+    this.#queue.write(data);
   }
+
+  #queue = null;
 }
 
 class Consumer {
-  constructor() {}
+  constructor(queue) {
+    this.#queue = queue;
+  }
+
   destroy(){
-    log('- csm destroy:', queue.read());
+    log('- csm destroy:', this.#queue.read());
   }
+
+  #queue = null;
 }
 
-let csm   = new Consumer();
+function main() {
+  const queue = new Queue(),
+        prd   = new Producer(queue),
+        csm   = new Consumer(queue);
 
-queue.on('data', async()=>{
-  csm.destroy();
-});
+  queue.on('data', ()=>csm.destroy());
 
-function main() {
-  const prd = new Producer();
-  for(let i=0; i<5; i++) {
-    prd.create(i);
-  }
+  for(let i=0; i<5; i++) prd.create(i);
 }
 
 main();

08-event/12-bind.js

@@ -0,0 +1,50 @@
+#!/usr/bin/env node
+
+// b = a + 10, 当 a 的值变化时，b 的值自动更新
+// b 绑定到 a 上了，下面是实现的代码
+
+const { EventEmitter } = require('events');
+
+class A extends EventEmitter {
+  constructor(value) {
+    super();
+    this.#value = value;
+    this.emit('change');
+  }
+
+  get value() { return this.#value; }
+  set value(value) {
+    this.#value = value;
+    this.emit('change');
+  }
+
+  #value = 0
+}
+
+class B {
+  constructor(obj) {
+    this.#value = obj.value + 10;
+    obj.on('change', () => this.#value = obj.value + 10);
+  }
+
+  get value() { return this.#value; }
+  set value(value) {
+    this.#value = value;
+    this.emit('change', value);
+  }
+
+  #value = 0
+}
+
+class App {
+  static main() {
+    const log = console.log;
+    const a = new A(10);
+    const b = new B(a);
+    log(b.value);  // 20
+    a.value = 20;
+    log(b.value);  // 30
+  }
+}
+
+App.main();